diff --git a/Makefile.am b/Makefile.am
index 1b9c092e4..d85167b01 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -379,7 +379,6 @@ i3_nagbar_i3_nagbar_LDADD = \
 
 i3_nagbar_i3_nagbar_SOURCES = \
 	i3-nagbar/atoms.xmacro \
-	i3-nagbar/i3-nagbar.h \
 	i3-nagbar/main.c
 
 i3bar_i3bar_CPPFLAGS = \
diff --git a/generate-command-parser.pl b/generate-command-parser.pl
index a017edab2..77502db7e 100755
--- a/generate-command-parser.pl
+++ b/generate-command-parser.pl
@@ -117,6 +117,7 @@ sub slurp {
 open(my $enumfh, '>', "GENERATED_${prefix}_enums.h");
 
 my %statenum;
+say $enumfh '#pragma once';
 say $enumfh 'typedef enum {';
 my $cnt = 0;
 for my $state (@keys, '__CALL') {
@@ -131,6 +132,7 @@ sub slurp {
 # Third step: Generate the call function.
 open(my $callfh, '>', "GENERATED_${prefix}_call.h");
 my $resultname = uc(substr($prefix, 0, 1)) . substr($prefix, 1) . 'ResultIR';
+say $callfh '#pragma once';
 say $callfh "static void GENERATED_call(const int call_identifier, struct $resultname *result) {";
 say $callfh '    switch (call_identifier) {';
 my $call_id = 0;
@@ -206,6 +208,7 @@ sub slurp {
 # Fourth step: Generate the token datastructures.
 
 open(my $tokfh, '>', "GENERATED_${prefix}_tokens.h");
+say $tokfh '#pragma once';
 
 for my $state (@keys) {
     my $tokens = $states{$state};
diff --git a/i3-config-wizard/main.c b/i3-config-wizard/main.c
index f999de308..9e07d1f7d 100644
--- a/i3-config-wizard/main.c
+++ b/i3-config-wizard/main.c
@@ -10,6 +10,8 @@
  */
 #include <config.h>
 
+#include "libi3.h"
+
 #if defined(__FreeBSD__)
 #include <sys/param.h>
 #endif
@@ -23,37 +25,31 @@
 #define _WITH_GETLINE
 #endif
 
-#include <stdio.h>
-#include <sys/types.h>
-#include <stdlib.h>
-#include <stdbool.h>
-#include <unistd.h>
-#include <string.h>
 #include <ctype.h>
-#include <errno.h>
 #include <err.h>
-#include <stdint.h>
+#include <errno.h>
+#include <fcntl.h>
 #include <getopt.h>
 #include <limits.h>
+#include <stdlib.h>
+#include <string.h>
 #include <sys/stat.h>
-#include <fcntl.h>
-#include <glob.h>
-#include <assert.h>
+#include <sys/types.h>
+#include <unistd.h>
 
 #include <xcb/xcb.h>
 #include <xcb/xcb_aux.h>
 #include <xcb/xcb_event.h>
 #include <xcb/xcb_keysyms.h>
-
-#include <xkbcommon/xkbcommon.h>
 #include <xkbcommon/xkbcommon-x11.h>
+#include <xkbcommon/xkbcommon.h>
 
 #define SN_API_NOT_YET_FROZEN 1
 #include <libsn/sn-launchee.h>
 
+#include <X11/XKBlib.h>
 #include <X11/Xlib.h>
 #include <X11/keysym.h>
-#include <X11/XKBlib.h>
 
 /* We need SYSCONFDIR for the path to the keycode config template, so raise an
  * error if it’s not defined for whatever reason */
@@ -69,7 +65,6 @@
 
 #include "xcb.h"
 xcb_visualtype_t *visual_type = NULL;
-#include "libi3.h"
 
 #define TEXT_PADDING logical_px(4)
 #define WIN_POS_X logical_px(490)
diff --git a/i3-dump-log/main.c b/i3-dump-log/main.c
index ba60d396e..e58b0c379 100644
--- a/i3-dump-log/main.c
+++ b/i3-dump-log/main.c
@@ -9,27 +9,22 @@
  */
 #include <config.h>
 
-#include <stdio.h>
+#include "libi3.h"
+#include "shmlog.h"
+
+#include <err.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <i3/ipc.h>
+#include <signal.h>
 #include <stdbool.h>
-#include <sys/types.h>
-#include <sys/socket.h>
-#include <sys/un.h>
+#include <stdint.h>
+#include <stdio.h>
 #include <stdlib.h>
-#include <unistd.h>
 #include <string.h>
-#include <errno.h>
-#include <err.h>
-#include <stdint.h>
-#include <getopt.h>
-#include <limits.h>
-#include <fcntl.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
-#include <signal.h>
-
-#include "libi3.h"
-#include "shmlog.h"
-#include <i3/ipc.h>
+#include <unistd.h>
 
 #if !defined(__OpenBSD__)
 static uint32_t offset_next_write;
diff --git a/i3-input/keysym2ucs.c b/i3-input/keysym2ucs.c
index 52bdc0444..80375099c 100644
--- a/i3-input/keysym2ucs.c
+++ b/i3-input/keysym2ucs.c
@@ -31,9 +31,10 @@
  * This software is in the public domain. Share and enjoy!
  */
 
-#include <xcb/xcb.h>
 #include "keysym2ucs.h"
 
+#include <xcb/xcb.h>
+
 struct codepair {
     unsigned short keysym;
     unsigned short ucs;
diff --git a/i3-input/main.c b/i3-input/main.c
index e495fe10a..dc38b8a6a 100644
--- a/i3-input/main.c
+++ b/i3-input/main.c
@@ -8,32 +8,26 @@
  *                  to i3.
  *
  */
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
-#include <sys/types.h>
 #include <stdlib.h>
-#include <stdbool.h>
-#include <unistd.h>
 #include <string.h>
-#include <errno.h>
-#include <err.h>
-#include <stdint.h>
-#include <getopt.h>
-#include <limits.h>
+#include <sys/types.h>
+#include <unistd.h>
 
 #include <xcb/xcb.h>
 #include <xcb/xcb_aux.h>
-#include <xcb/xcb_event.h>
 #include <xcb/xcb_keysyms.h>
 
 xcb_visualtype_t *visual_type = NULL;
+#include "i3-input.h"
+#include "keysym2ucs.h"
 #include "libi3.h"
 
 #include <X11/keysym.h>
 
-#include "keysym2ucs.h"
-
-#include "i3-input.h"
-
 #define MAX_WIDTH logical_px(500)
 #define BORDER logical_px(2)
 #define PADDING logical_px(2)
diff --git a/i3-msg/main.c b/i3-msg/main.c
index 3a8974161..0b0ef4e39 100644
--- a/i3-msg/main.c
+++ b/i3-msg/main.c
@@ -16,27 +16,17 @@
  */
 #include "libi3.h"
 
-#include <stdio.h>
+#include <err.h>
+#include <getopt.h>
+#include <i3/ipc.h>
 #include <stdbool.h>
-#include <sys/types.h>
-#include <sys/socket.h>
-#include <sys/un.h>
+#include <stdint.h>
+#include <stdio.h>
 #include <stdlib.h>
-#include <unistd.h>
 #include <string.h>
-#include <errno.h>
-#include <err.h>
-#include <stdint.h>
-#include <getopt.h>
-#include <limits.h>
+#include <unistd.h>
 
 #include <yajl/yajl_parse.h>
-#include <yajl/yajl_version.h>
-
-#include <xcb/xcb.h>
-#include <xcb/xcb_aux.h>
-
-#include <i3/ipc.h>
 
 /*
  * Having verboselog() and errorlog() is necessary when using libi3.
diff --git a/i3-nagbar/i3-nagbar.h b/i3-nagbar/i3-nagbar.h
deleted file mode 100644
index cb672bead..000000000
--- a/i3-nagbar/i3-nagbar.h
+++ /dev/null
@@ -1,18 +0,0 @@
-#pragma once
-
-#include <config.h>
-
-#include <err.h>
-
-#define die(...) errx(EXIT_FAILURE, __VA_ARGS__);
-#define FREE(pointer)   \
-    do {                \
-        free(pointer);  \
-        pointer = NULL; \
-    } while (0)
-
-#define xmacro(atom) xcb_atom_t A_##atom;
-#include "atoms.xmacro"
-#undef xmacro
-
-extern xcb_window_t root;
diff --git a/i3-nagbar/main.c b/i3-nagbar/main.c
index e59f5a6a3..51e5475c9 100644
--- a/i3-nagbar/main.c
+++ b/i3-nagbar/main.c
@@ -8,36 +8,33 @@
  * when the user has an error in their configuration file.
  *
  */
-#include <stdio.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <sys/wait.h>
-#include <stdlib.h>
-#include <stdbool.h>
-#include <unistd.h>
-#include <string.h>
-#include <errno.h>
+#include <config.h>
+
+#include "libi3.h"
+
 #include <err.h>
-#include <stdint.h>
+#include <fcntl.h>
 #include <getopt.h>
 #include <limits.h>
-#include <fcntl.h>
 #include <paths.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
 
+#include <xcb/randr.h>
 #include <xcb/xcb.h>
 #include <xcb/xcb_aux.h>
-#include <xcb/xcb_event.h>
-#include <xcb/randr.h>
 #include <xcb/xcb_cursor.h>
 
 xcb_visualtype_t *visual_type = NULL;
-#include "libi3.h"
 
 #define SN_API_NOT_YET_FROZEN 1
 #include <libsn/sn-launchee.h>
 
-#include "i3-nagbar.h"
-
 #define MSG_PADDING logical_px(8)
 #define BTN_PADDING logical_px(3)
 #define BTN_BORDER logical_px(3)
@@ -45,6 +42,12 @@ xcb_visualtype_t *visual_type = NULL;
 #define CLOSE_BTN_GAP logical_px(15)
 #define BAR_BORDER logical_px(2)
 
+#define xmacro(atom) xcb_atom_t A_##atom;
+#include "atoms.xmacro"
+#undef xmacro
+
+#define die(...) errx(EXIT_FAILURE, __VA_ARGS__);
+
 static char *argv0 = NULL;
 
 typedef struct {
@@ -314,8 +317,8 @@ static xcb_rectangle_t get_window_position(void) {
     goto free_resources;
 
 free_resources:
-    FREE(res);
-    FREE(primary);
+    free(res);
+    free(primary);
     return result;
 }
 
@@ -598,7 +601,7 @@ int main(int argc, char *argv[]) {
         free(event);
     }
 
-    FREE(pattern);
+    free(pattern);
     draw_util_surface_free(conn, &bar);
 
     return 0;
diff --git a/i3bar/include/common.h b/i3bar/include/common.h
index 222f42dd9..2d763133b 100644
--- a/i3bar/include/common.h
+++ b/i3bar/include/common.h
@@ -9,7 +9,6 @@
 
 #include <config.h>
 
-#include <stdbool.h>
 #include <xcb/xcb.h>
 #include <xcb/xproto.h>
 #include "libi3.h"
@@ -94,5 +93,4 @@ extern TAILQ_HEAD(statusline_head, status_block)
 #include "trayclients.h"
 #include "xcb.h"
 #include "configuration.h"
-#include "libi3.h"
 #include "parse_json_header.h"
diff --git a/i3bar/src/child.c b/i3bar/src/child.c
index e56145fac..871c23052 100644
--- a/i3bar/src/child.c
+++ b/i3bar/src/child.c
@@ -10,25 +10,21 @@
 #include "common.h"
 #include "yajl_utils.h"
 
-#include <stdlib.h>
-#include <unistd.h>
-#include <sys/types.h>
-#include <sys/wait.h>
-#include <signal.h>
-#include <stdio.h>
-#include <stdarg.h>
-#include <fcntl.h>
-#include <string.h>
-#include <errno.h>
 #include <err.h>
+#include <errno.h>
 #include <ev.h>
-#include <yajl/yajl_common.h>
-#include <yajl/yajl_parse.h>
-#include <yajl/yajl_version.h>
-#include <yajl/yajl_gen.h>
+#include <fcntl.h>
 #include <paths.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
 
-#include <xcb/xcb_keysyms.h>
+#include <yajl/yajl_gen.h>
+#include <yajl/yajl_parse.h>
 
 /* Global variables for child_*() */
 i3bar_child child;
diff --git a/i3bar/src/config.c b/i3bar/src/config.c
index 11d8e0a2d..c96277902 100644
--- a/i3bar/src/config.c
+++ b/i3bar/src/config.c
@@ -9,15 +9,12 @@
  */
 #include "common.h"
 
-#include <string.h>
-#include <stdlib.h>
 #include <stdio.h>
-#include <errno.h>
-#include <i3/ipc.h>
-#include <yajl/yajl_parse.h>
-#include <yajl/yajl_version.h>
+#include <stdlib.h>
+#include <string.h>
 
 #include <X11/Xlib.h>
+#include <yajl/yajl_parse.h>
 
 config_t config;
 static char *cur_key;
diff --git a/i3bar/src/ipc.c b/i3bar/src/ipc.c
index 37bdbac2b..f2c105ac3 100644
--- a/i3bar/src/ipc.c
+++ b/i3bar/src/ipc.c
@@ -9,16 +9,13 @@
  */
 #include "common.h"
 
-#include <stdlib.h>
-#include <stdio.h>
-#include <unistd.h>
-#include <stdint.h>
-#include <string.h>
 #include <errno.h>
-#include <sys/socket.h>
-#include <sys/un.h>
-#include <i3/ipc.h>
 #include <ev.h>
+#include <i3/ipc.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 #ifdef I3_ASAN_ENABLED
 #include <sanitizer/lsan_interface.h>
 #endif
diff --git a/i3bar/src/main.c b/i3bar/src/main.c
index 65cb00ff5..4e729341b 100644
--- a/i3bar/src/main.c
+++ b/i3bar/src/main.c
@@ -7,15 +7,13 @@
  */
 #include "common.h"
 
-#include <stdio.h>
-#include <i3/ipc.h>
-#include <string.h>
-#include <unistd.h>
-#include <stdlib.h>
-#include <errno.h>
 #include <ev.h>
 #include <getopt.h>
 #include <glob.h>
+#include <i3/ipc.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 
 struct ev_loop *main_loop;
 
diff --git a/i3bar/src/mode.c b/i3bar/src/mode.c
index 97087ce09..13d02110a 100644
--- a/i3bar/src/mode.c
+++ b/i3bar/src/mode.c
@@ -9,12 +9,10 @@
  */
 #include "common.h"
 
-#include <string.h>
 #include <stdlib.h>
-#include <stdio.h>
-#include <errno.h>
+#include <string.h>
+
 #include <yajl/yajl_parse.h>
-#include <yajl/yajl_version.h>
 
 /* A datatype to pass through the callbacks to save the state */
 struct mode_json_params {
diff --git a/i3bar/src/outputs.c b/i3bar/src/outputs.c
index 6ebb7cc6b..46b9c9548 100644
--- a/i3bar/src/outputs.c
+++ b/i3bar/src/outputs.c
@@ -9,13 +9,12 @@
  */
 #include "common.h"
 
-#include <string.h>
-#include <stdlib.h>
-#include <stdio.h>
 #include <errno.h>
-#include <i3/ipc.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
 #include <yajl/yajl_parse.h>
-#include <yajl/yajl_version.h>
 
 /* A datatype to pass through the callbacks to save the state */
 struct outputs_json_params {
diff --git a/i3bar/src/parse_json_header.c b/i3bar/src/parse_json_header.c
index 3d4c2a67f..c74a62fee 100644
--- a/i3bar/src/parse_json_header.c
+++ b/i3bar/src/parse_json_header.c
@@ -10,22 +10,10 @@
  */
 #include "common.h"
 
-#include <stdlib.h>
-#include <unistd.h>
-#include <sys/types.h>
-#include <sys/wait.h>
 #include <signal.h>
-#include <stdio.h>
-#include <fcntl.h>
 #include <string.h>
-#include <errno.h>
-#include <err.h>
-#include <ev.h>
-#include <stdbool.h>
-#include <stdint.h>
-#include <yajl/yajl_common.h>
+
 #include <yajl/yajl_parse.h>
-#include <yajl/yajl_version.h>
 
 static enum {
     KEY_VERSION,
diff --git a/i3bar/src/workspaces.c b/i3bar/src/workspaces.c
index 68686611a..bd56f5d09 100644
--- a/i3bar/src/workspaces.c
+++ b/i3bar/src/workspaces.c
@@ -9,12 +9,10 @@
  */
 #include "common.h"
 
-#include <string.h>
 #include <stdlib.h>
-#include <stdio.h>
-#include <errno.h>
+#include <string.h>
+
 #include <yajl/yajl_parse.h>
-#include <yajl/yajl_version.h>
 
 /* A datatype to pass through the callbacks to save the state */
 struct workspaces_json_params {
diff --git a/i3bar/src/xcb.c b/i3bar/src/xcb.c
index 15c6f82fa..9a599e36a 100644
--- a/i3bar/src/xcb.c
+++ b/i3bar/src/xcb.c
@@ -9,26 +9,15 @@
  */
 #include "common.h"
 
-#include <xcb/xcb.h>
-#include <xcb/xkb.h>
-#include <xcb/xproto.h>
-#include <xcb/xcb_aux.h>
-#include <xcb/xcb_cursor.h>
-
-#include <stdio.h>
+#include <err.h>
+#include <ev.h>
+#include <i3/ipc.h>
 #include <stdlib.h>
-#include <unistd.h>
-#include <fcntl.h>
 #include <string.h>
-#include <i3/ipc.h>
-#include <ev.h>
-#include <errno.h>
-#include <limits.h>
-#include <err.h>
 
-#include <X11/Xlib.h>
-#include <X11/XKBlib.h>
-#include <X11/extensions/XKB.h>
+#include <xcb/xcb_aux.h>
+#include <xcb/xcb_cursor.h>
+#include <xcb/xkb.h>
 
 #ifdef I3_ASAN_ENABLED
 #include <sanitizer/lsan_interface.h>
diff --git a/include/all.h b/include/all.h
index aa2b5b250..551119441 100644
--- a/include/all.h
+++ b/include/all.h
@@ -15,31 +15,24 @@
 #include <config.h>
 
 #include <assert.h>
+#include <err.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdarg.h>
 #include <stdbool.h>
-#include <stdlib.h>
+#include <stdint.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
-#include <locale.h>
-#include <getopt.h>
-#include <unistd.h>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <glob.h>
-#include <errno.h>
-#include <err.h>
-#include <stdint.h>
-#include <inttypes.h>
-#include <math.h>
-#include <limits.h>
 
 #include <xcb/xcb.h>
 #include <xcb/xcb_aux.h>
-#include <xcb/xcb_keysyms.h>
 #include <xcb/xcb_icccm.h>
+#include <xcb/xcb_keysyms.h>
 
-#include <yajl/yajl_gen.h>
-#include <yajl/yajl_version.h>
-
+#include "libi3.h"
 #include "data.h"
 #include "util.h"
 #include "ipc.h"
@@ -72,7 +65,6 @@
 #include "ewmh.h"
 #include "assignments.h"
 #include "regex.h"
-#include "libi3.h"
 #include "startup.h"
 #include "scratchpad.h"
 #include "commands.h"
diff --git a/include/configuration.h b/include/configuration.h
index cd5daa8e1..53973462d 100644
--- a/include/configuration.h
+++ b/include/configuration.h
@@ -12,9 +12,6 @@
  */
 #pragma once
 
-#include "libi3.h"
-
-#include <stdbool.h>
 #include "queue.h"
 #include "i3.h"
 
diff --git a/include/data.h b/include/data.h
index 2dfb86cd4..18490f4b7 100644
--- a/include/data.h
+++ b/include/data.h
@@ -9,13 +9,10 @@
  */
 #pragma once
 
-#include "libi3.h"
-
 #define SN_API_NOT_YET_FROZEN 1
 #include <libsn/sn-launcher.h>
 
 #include <xcb/randr.h>
-#include <stdbool.h>
 #include <pcre.h>
 #include <sys/time.h>
 
diff --git a/include/floating.h b/include/floating.h
index 8e60f78c7..612874fcf 100644
--- a/include/floating.h
+++ b/include/floating.h
@@ -25,7 +25,7 @@ typedef enum { BORDER_LEFT = (1 << 0),
  * floating_windows list of the workspace.
  *
  */
-void floating_enable(Con *con, bool automatic);
+bool floating_enable(Con *con, bool automatic);
 
 /**
  * Disables floating mode for the given container by re-attaching the container
diff --git a/include/ipc.h b/include/ipc.h
index 8ea9fd2e4..bc5929ecf 100644
--- a/include/ipc.h
+++ b/include/ipc.h
@@ -12,7 +12,6 @@
 #include <config.h>
 
 #include <ev.h>
-#include <stdbool.h>
 #include <yajl/yajl_gen.h>
 #include <yajl/yajl_parse.h>
 
diff --git a/include/log.h b/include/log.h
index 5c530231d..d3c3e3f3e 100644
--- a/include/log.h
+++ b/include/log.h
@@ -11,9 +11,6 @@
 
 #include <config.h>
 
-#include <stdarg.h>
-#include <stdbool.h>
-
 /* We will include libi3.h which define its own version of LOG, ELOG.
  * We want *our* version, so we undef the libi3 one. */
 #if defined(LOG)
diff --git a/include/shmlog.h b/include/shmlog.h
index dc8081f13..7b7e133a6 100644
--- a/include/shmlog.h
+++ b/include/shmlog.h
@@ -12,7 +12,6 @@
 
 #include <config.h>
 
-#include <stdint.h>
 #if !defined(__OpenBSD__)
 #include <pthread.h>
 #endif
diff --git a/include/xinerama.h b/include/xinerama.h
index f01ee568c..52a5db335 100644
--- a/include/xinerama.h
+++ b/include/xinerama.h
@@ -13,8 +13,6 @@
 
 #include <config.h>
 
-#include "data.h"
-
 /**
  * We have just established a connection to the X server and need the initial
  * Xinerama information to setup workspaces for each screen.
diff --git a/libi3/dpi.c b/libi3/dpi.c
index d15e35be7..dec38bc86 100644
--- a/libi3/dpi.c
+++ b/libi3/dpi.c
@@ -9,6 +9,7 @@
 
 #include <math.h>
 #include <stdlib.h>
+
 #include <xcb/xcb_xrm.h>
 
 static long dpi;
diff --git a/libi3/draw_util.c b/libi3/draw_util.c
index 092ac967b..313dc29ac 100644
--- a/libi3/draw_util.c
+++ b/libi3/draw_util.c
@@ -9,11 +9,10 @@
 #include "libi3.h"
 
 #include <stdlib.h>
-#include <err.h>
 #include <string.h>
+
 #include <xcb/xcb.h>
 #include <xcb/xcb_aux.h>
-#include <cairo/cairo-xcb.h>
 
 /* The default visual_type to use if none is specified when creating the surface. Must be defined globally. */
 extern xcb_visualtype_t *visual_type;
diff --git a/libi3/fake_configure_notify.c b/libi3/fake_configure_notify.c
index 145f45122..5d87c3dac 100644
--- a/libi3/fake_configure_notify.c
+++ b/libi3/fake_configure_notify.c
@@ -8,7 +8,6 @@
 #include "libi3.h"
 
 #include <stdlib.h>
-#include <stdbool.h>
 
 #include <xcb/xcb.h>
 #include <xcb/xproto.h>
diff --git a/libi3/font.c b/libi3/font.c
index e01edb533..477509d03 100644
--- a/libi3/font.c
+++ b/libi3/font.c
@@ -8,14 +8,12 @@
 #include "libi3.h"
 
 #include <assert.h>
+#include <cairo/cairo-xcb.h>
+#include <err.h>
+#include <pango/pangocairo.h>
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
-#include <stdbool.h>
-#include <err.h>
-
-#include <cairo/cairo-xcb.h>
-#include <pango/pangocairo.h>
 
 static const i3Font *savedFont = NULL;
 
diff --git a/libi3/format_placeholders.c b/libi3/format_placeholders.c
index 770e383d7..71870a7b1 100644
--- a/libi3/format_placeholders.c
+++ b/libi3/format_placeholders.c
@@ -8,7 +8,6 @@
 #include "libi3.h"
 
 #include <stdlib.h>
-#include <stdint.h>
 #include <string.h>
 
 #ifndef CS_STARTS_WITH
diff --git a/libi3/g_utf8_make_valid.c b/libi3/g_utf8_make_valid.c
index b15873b37..71beafd30 100644
--- a/libi3/g_utf8_make_valid.c
+++ b/libi3/g_utf8_make_valid.c
@@ -19,8 +19,8 @@
 
 #include "libi3.h"
 
-#include <string.h>
 #include <glib.h>
+#include <string.h>
 
 /* Copied from:
  * https://gitlab.gnome.org/GNOME/glib/blob/f928dfdf57bf92c883b53b16d7a9d49add504f52/glib/gutf8.c#L1752-1815 */
diff --git a/libi3/get_colorpixel.c b/libi3/get_colorpixel.c
index 09ce70b98..efc86fac1 100644
--- a/libi3/get_colorpixel.c
+++ b/libi3/get_colorpixel.c
@@ -6,12 +6,11 @@
  *
  */
 #include "libi3.h"
+#include "queue.h"
 
-#include <stdlib.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
-
-#include "queue.h"
 struct Colorpixel {
     char hex[8];
     uint32_t pixel;
diff --git a/libi3/get_exe_path.c b/libi3/get_exe_path.c
index 430fb2e07..3b46ef82f 100644
--- a/libi3/get_exe_path.c
+++ b/libi3/get_exe_path.c
@@ -7,12 +7,10 @@
  */
 #include "libi3.h"
 
-#include <unistd.h>
-#include <string.h>
-#include <stdio.h>
-#include <limits.h>
-#include <stdlib.h>
 #include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 
 /*
  * This function returns the absolute path to the executable it is running in.
diff --git a/libi3/get_mod_mask.c b/libi3/get_mod_mask.c
index 98031d4ce..92af456df 100644
--- a/libi3/get_mod_mask.c
+++ b/libi3/get_mod_mask.c
@@ -9,6 +9,7 @@
 
 #include <stdint.h>
 #include <stdlib.h>
+
 #include <xcb/xcb.h>
 #include <xcb/xcb_keysyms.h>
 
diff --git a/libi3/get_process_filename.c b/libi3/get_process_filename.c
index 7e2ecbd24..21429ec36 100644
--- a/libi3/get_process_filename.c
+++ b/libi3/get_process_filename.c
@@ -7,17 +7,11 @@
  */
 #include "libi3.h"
 
-#include <assert.h>
-#include <stdint.h>
-#include <stdlib.h>
-#include <string.h>
-#include <stdbool.h>
 #include <err.h>
-#include <sys/stat.h>
-#include <sys/types.h>
 #include <pwd.h>
+#include <stdlib.h>
+#include <sys/stat.h>
 #include <unistd.h>
-#include <err.h>
 
 /*
  * Returns the name of a temporary file with the specified prefix.
diff --git a/libi3/ipc_connect.c b/libi3/ipc_connect.c
index f659a1a47..871fe083b 100644
--- a/libi3/ipc_connect.c
+++ b/libi3/ipc_connect.c
@@ -7,14 +7,12 @@
  */
 #include "libi3.h"
 
-#include <sys/types.h>
-#include <sys/socket.h>
-#include <sys/un.h>
-#include <string.h>
 #include <err.h>
-#include <stdlib.h>
-#include <unistd.h>
 #include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
 
 /*
  * Connects to the i3 IPC socket and returns the file descriptor for the
diff --git a/libi3/ipc_recv_message.c b/libi3/ipc_recv_message.c
index 84da5aa36..516405b00 100644
--- a/libi3/ipc_recv_message.c
+++ b/libi3/ipc_recv_message.c
@@ -7,15 +7,12 @@
  */
 #include "libi3.h"
 
-#include <string.h>
-#include <stdlib.h>
-#include <stdio.h>
-#include <stdint.h>
-#include <unistd.h>
 #include <errno.h>
-#include <inttypes.h>
-
 #include <i3/ipc.h>
+#include <inttypes.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
 
 /*
  * Reads a message from the given socket file descriptor and stores its length
diff --git a/libi3/ipc_send_message.c b/libi3/ipc_send_message.c
index c2cc0127d..4faeea7fd 100644
--- a/libi3/ipc_send_message.c
+++ b/libi3/ipc_send_message.c
@@ -7,14 +7,8 @@
  */
 #include "libi3.h"
 
-#include <string.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <stdint.h>
-#include <err.h>
-#include <errno.h>
-
 #include <i3/ipc.h>
+#include <stdint.h>
 
 /*
  * Formats a message (payload) of the given size and type and sends it to i3 via
diff --git a/libi3/is_debug_build.c b/libi3/is_debug_build.c
index 52187bdae..cb53407ec 100644
--- a/libi3/is_debug_build.c
+++ b/libi3/is_debug_build.c
@@ -8,7 +8,6 @@
 #include "libi3.h"
 
 #include <string.h>
-#include <stdbool.h>
 
 /*
  * Returns true if this version of i3 is a debug build (anything which is not a
diff --git a/libi3/root_atom_contents.c b/libi3/root_atom_contents.c
index d6394d4bf..6feb31bc8 100644
--- a/libi3/root_atom_contents.c
+++ b/libi3/root_atom_contents.c
@@ -7,12 +7,9 @@
  */
 #include "libi3.h"
 
-#include <stdio.h>
-#include <string.h>
-#include <stdbool.h>
-#include <limits.h>
-#include <stdlib.h>
 #include <math.h>
+#include <stdlib.h>
+#include <string.h>
 
 #include <xcb/xcb.h>
 #include <xcb/xcb_aux.h>
diff --git a/libi3/safewrappers.c b/libi3/safewrappers.c
index fdea636ee..767a0f05e 100644
--- a/libi3/safewrappers.c
+++ b/libi3/safewrappers.c
@@ -7,13 +7,11 @@
  */
 #include "libi3.h"
 
-#include <string.h>
-#include <stdlib.h>
-#include <stdarg.h>
-#include <unistd.h>
-#include <stdio.h>
 #include <err.h>
 #include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 
 /*
  * The s* functions (safe) are wrappers around malloc, strdup, …, which exits if one of
diff --git a/libi3/string.c b/libi3/string.c
index 9efa36903..da18c550b 100644
--- a/libi3/string.c
+++ b/libi3/string.c
@@ -11,11 +11,10 @@
  */
 #include "libi3.h"
 
+#include <glib.h>
 #include <stdlib.h>
 #include <string.h>
 
-#include <glib.h>
-
 struct _i3String {
     char *utf8;
     xcb_char2b_t *ucs2;
diff --git a/libi3/strndup.c b/libi3/strndup.c
index e215a76fd..a0e87cf6e 100644
--- a/libi3/strndup.c
+++ b/libi3/strndup.c
@@ -7,7 +7,6 @@
  */
 #include "libi3.h"
 
-#include <sys/types.h>
 #include <string.h>
 
 #ifndef HAVE_strndup
diff --git a/libi3/ucs2_conversion.c b/libi3/ucs2_conversion.c
index c651cdb32..c74672395 100644
--- a/libi3/ucs2_conversion.c
+++ b/libi3/ucs2_conversion.c
@@ -8,7 +8,6 @@
 #include "libi3.h"
 
 #include <err.h>
-#include <errno.h>
 #include <iconv.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/release.sh b/release.sh
index 095bc50b5..3335aa4a0 100755
--- a/release.sh
+++ b/release.sh
@@ -1,8 +1,8 @@
 #!/bin/zsh
 # This script is used to prepare a new release of i3.
 
-export RELEASE_VERSION="4.17"
-export PREVIOUS_VERSION="4.16"
+export RELEASE_VERSION="4.19"
+export PREVIOUS_VERSION="4.18"
 export RELEASE_BRANCH="next"
 
 if [ ! -e "../i3.github.io" ]
@@ -69,11 +69,9 @@ cp build/i3-${RELEASE_VERSION}.tar.bz2 .
 
 echo "Differences in the release tarball file lists:"
 
-diff -u \
+diff --color -u \
 	<(tar tf ../i3-${PREVIOUS_VERSION}.tar.bz2 | sed "s,i3-${PREVIOUS_VERSION}/,,g" | sort) \
-	<(tar tf    i3-${RELEASE_VERSION}.tar.bz2  | sed "s,i3-${RELEASE_VERSION}/,,g"  | sort) \
-	| colordiff
-
+	<(tar tf    i3-${RELEASE_VERSION}.tar.bz2  | sed "s,i3-${RELEASE_VERSION}/,,g"  | sort)
 
 gpg --armor -b i3-${RELEASE_VERSION}.tar.bz2
 
@@ -130,7 +128,7 @@ RUN dpkg-buildpackage -S -sa -j8
 EOT
 
 CONTAINER_NAME=$(echo "i3-${TMPDIR}" | sed 's,/,,g')
-docker build -t i3 .
+docker build --no-cache -t i3 .
 for file in $(docker run --name "${CONTAINER_NAME}" i3 /bin/sh -c "ls /usr/src/i3*_${RELEASE_VERSION}*")
 do
 	docker cp "${CONTAINER_NAME}:${file}" ${TMPDIR}/debian/
diff --git a/src/bindings.c b/src/bindings.c
index 03dc23065..e29f2c2dc 100644
--- a/src/bindings.c
+++ b/src/bindings.c
@@ -8,8 +8,10 @@
  */
 #include "all.h"
 
-#include <xkbcommon/xkbcommon.h>
+#include <math.h>
+
 #include <xkbcommon/xkbcommon-x11.h>
+#include <xkbcommon/xkbcommon.h>
 
 static struct xkb_context *xkb_context;
 static struct xkb_keymap *xkb_keymap;
diff --git a/src/click.c b/src/click.c
index 12e391b53..64d78315d 100644
--- a/src/click.c
+++ b/src/click.c
@@ -10,11 +10,6 @@
 #include "all.h"
 
 #include <time.h>
-#include <math.h>
-
-#include <xcb/xcb_icccm.h>
-
-#include <X11/XKBlib.h>
 
 typedef enum { CLICK_BORDER = 0,
                CLICK_DECORATION = 1,
diff --git a/src/commands.c b/src/commands.c
index 69bb426d5..d5f526621 100644
--- a/src/commands.c
+++ b/src/commands.c
@@ -8,14 +8,11 @@
  *
  */
 #include "all.h"
+#include "shmlog.h"
 
+#include <fcntl.h>
 #include <stdint.h>
-#include <float.h>
-#include <stdarg.h>
 #include <unistd.h>
-#include <fcntl.h>
-
-#include "shmlog.h"
 
 // Macros to make the YAJL API a bit easier to use.
 #define y(x, ...) (cmd_output->json_gen != NULL ? yajl_gen_##x(cmd_output->json_gen, ##__VA_ARGS__) : 0)
diff --git a/src/commands_parser.c b/src/commands_parser.c
index 2fd763095..6c7914151 100644
--- a/src/commands_parser.c
+++ b/src/commands_parser.c
@@ -25,13 +25,6 @@
  */
 #include "all.h"
 
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <unistd.h>
-#include <stdbool.h>
-#include <stdint.h>
-
 // Macros to make the YAJL API a bit easier to use.
 #define y(x, ...) (command_output.json_gen != NULL ? yajl_gen_##x(command_output.json_gen, ##__VA_ARGS__) : 0)
 #define ystr(str) (command_output.json_gen != NULL ? yajl_gen_string(command_output.json_gen, (unsigned char *)str, strlen(str)) : 0)
diff --git a/src/con.c b/src/con.c
index d9aaa5e5d..52f5afd88 100644
--- a/src/con.c
+++ b/src/con.c
@@ -10,7 +10,6 @@
  *
  */
 #include "all.h"
-
 #include "yajl_utils.h"
 
 static void con_on_remove_child(Con *con);
@@ -92,8 +91,8 @@ void con_free(Con *con) {
         FREE(mark->name);
         FREE(mark);
     }
-    free(con);
     DLOG("con %p freed\n", con);
+    free(con);
 }
 
 static void _con_attach(Con *con, Con *parent, Con *previous, bool ignore_focus) {
diff --git a/src/config_directives.c b/src/config_directives.c
index cf81cc160..52362547a 100644
--- a/src/config_directives.c
+++ b/src/config_directives.c
@@ -9,9 +9,6 @@
  */
 #include "all.h"
 
-#include <float.h>
-#include <stdarg.h>
-
 /*******************************************************************************
  * Criteria functions.
  ******************************************************************************/
diff --git a/src/config_parser.c b/src/config_parser.c
index f120cfa36..f78e75f83 100644
--- a/src/config_parser.c
+++ b/src/config_parser.c
@@ -25,16 +25,17 @@
  */
 #include "all.h"
 
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <unistd.h>
-#include <stdbool.h>
-#include <stdint.h>
+#include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
-#include <sys/stat.h>
-#include <fcntl.h>
+#include <unistd.h>
+
 #include <xcb/xcb_xrm.h>
 
 // Macros to make the YAJL API a bit easier to use.
diff --git a/src/display_version.c b/src/display_version.c
index e44540e08..32250c155 100644
--- a/src/display_version.c
+++ b/src/display_version.c
@@ -10,13 +10,9 @@
  */
 #include "all.h"
 
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <sys/wait.h>
-#include <sys/socket.h>
-#include <sys/un.h>
 #include <fcntl.h>
 #include <time.h>
+#include <unistd.h>
 
 static bool human_readable_key, loaded_config_file_name_key;
 static char *human_readable_version, *loaded_config_file_name;
diff --git a/src/floating.c b/src/floating.c
index fd313a521..02e6ac3b3 100644
--- a/src/floating.c
+++ b/src/floating.c
@@ -9,6 +9,8 @@
  */
 #include "all.h"
 
+#include <math.h>
+
 #ifndef MAX
 #define MAX(x, y) ((x) > (y) ? (x) : (y))
 #endif
@@ -221,22 +223,22 @@ void floating_check_size(Con *floating_con, bool prefer_height) {
     }
 }
 
-void floating_enable(Con *con, bool automatic) {
+bool floating_enable(Con *con, bool automatic) {
     bool set_focus = (con == focused);
 
     if (con_is_docked(con)) {
         LOG("Container is a dock window, not enabling floating mode.\n");
-        return;
+        return false;
     }
 
     if (con_is_floating(con)) {
         LOG("Container is already in floating mode, not doing anything.\n");
-        return;
+        return false;
     }
 
     if (con->type == CT_WORKSPACE) {
         LOG("Container is a workspace, not enabling floating mode.\n");
-        return;
+        return false;
     }
 
     Con *focus_head_placeholder = NULL;
@@ -419,6 +421,7 @@ void floating_enable(Con *con, bool automatic) {
 
     floating_set_hint_atom(nc, true);
     ipc_send_window_event("floating", con);
+    return true;
 }
 
 void floating_disable(Con *con) {
diff --git a/src/handlers.c b/src/handlers.c
index d6d6e20bc..b74e589dc 100644
--- a/src/handlers.c
+++ b/src/handlers.c
@@ -10,9 +10,9 @@
  */
 #include "all.h"
 
-#include <time.h>
-#include <float.h>
 #include <sys/time.h>
+#include <time.h>
+
 #include <xcb/randr.h>
 #define SN_API_NOT_YET_FROZEN 1
 #include <libsn/sn-monitor.h>
@@ -841,12 +841,13 @@ static void handle_client_message(xcb_client_message_event_t *event) {
              * let's float it and make it sticky. */
             DLOG("The window was requested to be visible on all workspaces, making it sticky and floating.\n");
 
-            floating_enable(con, false);
-            con->floating = FLOATING_AUTO_ON;
+            if (floating_enable(con, false)) {
+                con->floating = FLOATING_AUTO_ON;
 
-            con->sticky = true;
-            ewmh_update_sticky(con->window->id, true);
-            output_push_sticky_windows(focused);
+                con->sticky = true;
+                ewmh_update_sticky(con->window->id, true);
+                output_push_sticky_windows(focused);
+            }
         } else {
             Con *ws = ewmh_get_workspace_by_index(index);
             if (ws == NULL) {
diff --git a/src/ipc.c b/src/ipc.c
index e2b972559..faa2fbc09 100644
--- a/src/ipc.c
+++ b/src/ipc.c
@@ -7,16 +7,19 @@
  * ipc.c: UNIX domain socket IPC (initialization, client handling, protocol).
  *
  */
-#include "all.h"
 
+#include "all.h"
 #include "yajl_utils.h"
 
+#include <ev.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <locale.h>
 #include <stdint.h>
 #include <sys/socket.h>
 #include <sys/un.h>
-#include <fcntl.h>
-#include <libgen.h>
-#include <ev.h>
+#include <unistd.h>
+
 #include <yajl/yajl_gen.h>
 #include <yajl/yajl_parse.h>
 
diff --git a/src/load_layout.c b/src/load_layout.c
index acc83fb5c..a9c9678f9 100644
--- a/src/load_layout.c
+++ b/src/load_layout.c
@@ -10,10 +10,9 @@
  */
 #include "all.h"
 
-#include <yajl/yajl_common.h>
-#include <yajl/yajl_gen.h>
+#include <locale.h>
+
 #include <yajl/yajl_parse.h>
-#include <yajl/yajl_version.h>
 
 /* TODO: refactor the whole parsing thing */
 
diff --git a/src/log.c b/src/log.c
index 31db8b33c..326f82b8c 100644
--- a/src/log.c
+++ b/src/log.c
@@ -9,27 +9,24 @@
  */
 #include <config.h>
 
+#include "all.h"
+#include "shmlog.h"
+
+#include <errno.h>
+#include <fcntl.h>
 #include <stdarg.h>
-#include <stdio.h>
-#include <string.h>
 #include <stdbool.h>
+#include <stdio.h>
 #include <stdlib.h>
-#include <sys/time.h>
-#include <unistd.h>
-#include <fcntl.h>
+#include <string.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
-#include <errno.h>
+#include <sys/time.h>
+#include <unistd.h>
 #if !defined(__OpenBSD__)
 #include <pthread.h>
 #endif
 
-#include "util.h"
-#include "log.h"
-#include "i3.h"
-#include "libi3.h"
-#include "shmlog.h"
-
 #if defined(__APPLE__)
 #include <sys/sysctl.h>
 #endif
diff --git a/src/main.c b/src/main.c
index 369f2f66d..4f4c3fd6d 100644
--- a/src/main.c
+++ b/src/main.c
@@ -8,18 +8,22 @@
  *
  */
 #include "all.h"
+#include "shmlog.h"
 
 #include <ev.h>
 #include <fcntl.h>
-#include <sys/types.h>
-#include <sys/socket.h>
-#include <sys/un.h>
-#include <sys/time.h>
-#include <sys/resource.h>
+#include <getopt.h>
+#include <libgen.h>
+#include <locale.h>
+#include <signal.h>
 #include <sys/mman.h>
+#include <sys/resource.h>
+#include <sys/socket.h>
 #include <sys/stat.h>
-#include <libgen.h>
-#include "shmlog.h"
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <unistd.h>
 
 #ifdef I3_ASAN_ENABLED
 #include <sanitizer/lsan_interface.h>
diff --git a/src/manage.c b/src/manage.c
index 4e2803a5f..dc60294f7 100644
--- a/src/manage.c
+++ b/src/manage.c
@@ -9,10 +9,6 @@
  */
 #include "all.h"
 
-#include "yajl_utils.h"
-
-#include <yajl/yajl_gen.h>
-
 /*
  * Match frame and window depth. This is needed because X will refuse to reparent a
  * window whose background is ParentRelative under a window with a different depth.
@@ -537,8 +533,9 @@ void manage_window(xcb_window_t window, xcb_get_window_attributes_cookie_t cooki
          * was not specified */
         bool automatic_border = (motif_border_style == BS_NORMAL);
 
-        floating_enable(nc, automatic_border);
-        nc->floating = FLOATING_AUTO_ON;
+        if (floating_enable(nc, automatic_border)) {
+            nc->floating = FLOATING_AUTO_ON;
+        }
     }
 
     /* explicitly set the border width to the default */
diff --git a/src/randr.c b/src/randr.c
index b163eca7d..56b0707fc 100644
--- a/src/randr.c
+++ b/src/randr.c
@@ -12,6 +12,7 @@
 #include "all.h"
 
 #include <time.h>
+
 #include <xcb/randr.h>
 
 /* Pointer to the result of the query for primary output */
diff --git a/src/render.c b/src/render.c
index 79bf7eb49..a9803d16e 100644
--- a/src/render.c
+++ b/src/render.c
@@ -10,6 +10,8 @@
  */
 #include "all.h"
 
+#include <math.h>
+
 /* Forward declarations */
 static int *precalculate_sizes(Con *con, render_params *p);
 static void render_root(Con *con, Con *fullscreen);
diff --git a/src/sd-daemon.c b/src/sd-daemon.c
index 28a88bfd7..84761025b 100644
--- a/src/sd-daemon.c
+++ b/src/sd-daemon.c
@@ -28,21 +28,21 @@
 #define _GNU_SOURCE
 #endif
 
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <sys/socket.h>
-#include <sys/un.h>
-#include <sys/fcntl.h>
-#include <netinet/in.h>
-#include <stdlib.h>
+#include "sd-daemon.h"
+
 #include <errno.h>
-#include <unistd.h>
-#include <string.h>
+#include <netinet/in.h>
 #include <stdarg.h>
-#include <stdio.h>
 #include <stddef.h>
-
-#include "sd-daemon.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/fcntl.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <unistd.h>
 
 int sd_listen_fds(int unset_environment) {
     int r, fd;
diff --git a/src/sighandler.c b/src/sighandler.c
index 86921b400..c1e6094f2 100644
--- a/src/sighandler.c
+++ b/src/sighandler.c
@@ -7,14 +7,9 @@
  */
 #include "all.h"
 
-#include <ev.h>
-#include <iconv.h>
 #include <signal.h>
 #include <sys/wait.h>
-
-#include <xcb/xcb_event.h>
-
-#include <X11/keysym.h>
+#include <unistd.h>
 
 typedef struct dialog_t {
     xcb_window_t id;
diff --git a/src/startup.c b/src/startup.c
index e994e0a8d..9b0576e8a 100644
--- a/src/startup.c
+++ b/src/startup.c
@@ -11,12 +11,12 @@
  *
  */
 #include "all.h"
-
 #include "sd-daemon.h"
 
+#include <paths.h>
 #include <sys/types.h>
 #include <sys/wait.h>
-#include <paths.h>
+#include <unistd.h>
 
 #define SN_API_NOT_YET_FROZEN 1
 #include <libsn/sn-launcher.h>
diff --git a/src/util.c b/src/util.c
index 3544297c9..6d8d2ee75 100644
--- a/src/util.c
+++ b/src/util.c
@@ -10,19 +10,16 @@
  */
 #include "all.h"
 
+#include <ctype.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <libgen.h>
+#include <locale.h>
 #include <sys/wait.h>
-#include <stdarg.h>
+#include <unistd.h>
 #if defined(__OpenBSD__)
 #include <sys/cdefs.h>
 #endif
-#include <fcntl.h>
-#include <pwd.h>
-#include <yajl/yajl_version.h>
-#include <libgen.h>
-#include <ctype.h>
-
-#define SN_API_NOT_YET_FROZEN 1
-#include <libsn/sn-launcher.h>
 
 int min(int a, int b) {
     return (a < b ? a : b);
diff --git a/src/window.c b/src/window.c
index d84f8869a..bee3fa668 100644
--- a/src/window.c
+++ b/src/window.c
@@ -9,6 +9,8 @@
  */
 #include "all.h"
 
+#include <math.h>
+
 /*
  * Frees an i3Window and all its members.
  *
diff --git a/src/x.c b/src/x.c
index 712cf89c2..e89f52132 100644
--- a/src/x.c
+++ b/src/x.c
@@ -10,6 +10,8 @@
  */
 #include "all.h"
 
+#include <unistd.h>
+
 #ifndef MAX
 #define MAX(x, y) ((x) > (y) ? (x) : (y))
 #endif
diff --git a/src/xcursor.c b/src/xcursor.c
index cffb094b1..cb98399fa 100644
--- a/src/xcursor.c
+++ b/src/xcursor.c
@@ -9,13 +9,12 @@
  */
 #include <config.h>
 
+#include "all.h"
+
 #include <assert.h>
 #include <err.h>
-#include <xcb/xcb_cursor.h>
 
-#include "i3.h"
-#include "xcb.h"
-#include "xcursor.h"
+#include <xcb/xcb_cursor.h>
 
 static xcb_cursor_context_t *ctx;
 static xcb_cursor_t cursors[XCURSOR_CURSOR_MAX];
diff --git a/testcases/inject_randr1.5.c b/testcases/inject_randr1.5.c
index 819c029ba..9c0b73d41 100644
--- a/testcases/inject_randr1.5.c
+++ b/testcases/inject_randr1.5.c
@@ -16,15 +16,17 @@
 
 #include <ev.h>
 #include <fcntl.h>
-#include <sys/types.h>
-#include <sys/socket.h>
-#include <sys/un.h>
-#include <sys/time.h>
-#include <sys/resource.h>
+#include <getopt.h>
+#include <libgen.h>
 #include <sys/mman.h>
+#include <sys/resource.h>
+#include <sys/socket.h>
 #include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/un.h>
 #include <sys/wait.h>
-#include <libgen.h>
+#include <unistd.h>
 
 static void uds_connection_cb(EV_P_ ev_io *w, int revents);
 static void read_client_setup_request_cb(EV_P_ ev_io *w, int revents);
diff --git a/testcases/t/310-client-message-sticky.t b/testcases/t/310-client-message-sticky.t
new file mode 100644
index 000000000..0e7d8b7c3
--- /dev/null
+++ b/testcases/t/310-client-message-sticky.t
@@ -0,0 +1,70 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • https://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • https://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • https://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Verify that _NET_WM_DESKTOP sticky requests do not conflict with dock
+# clients, resulting in a crash
+# Ticket: #4039
+# Bug still in: 4.18-238-g4d55bba7f
+use i3test;
+
+sub send_sticky_request {
+    my ($win) = @_;
+
+    my $msg = pack "CCSLLLLLL",
+        X11::XCB::CLIENT_MESSAGE, # response_type
+        32, # format
+        0, # sequence
+        $win->id, # window
+        $x->atom(name => '_NET_WM_DESKTOP')->id, # message type
+        hex '0xFFFFFFFF', # data32[0] = NET_WM_DESKTOP_ALL
+        0, # data32[1]
+        0, # data32[2]
+        0, # data32[3]
+        0; # data32[4]
+
+    $x->send_event(0, $x->get_root_window(), X11::XCB::EVENT_MASK_SUBSTRUCTURE_REDIRECT, $msg);
+}
+
+# Test the normal functionality first
+my $ws = fresh_workspace;
+my $win = open_window;
+
+is(@{get_ws($ws)->{floating_nodes}}, 0, 'No floating windows yet');
+send_sticky_request($win);
+sync_with_i3;
+
+is(@{get_ws($ws)->{floating_nodes}}, 1, 'One floating (sticky) window');
+$ws = fresh_workspace;
+is(@{get_ws($ws)->{floating_nodes}}, 1, 'Sticky window in new workspace');
+
+# See #4039
+kill_all_windows;
+$win = open_window({
+    window_type => $x->atom(name => '_NET_WM_WINDOW_TYPE_DOCK')
+});
+
+send_sticky_request($win);
+sync_with_i3;
+is(@{get_ws($ws)->{floating_nodes}}, 0, 'Dock client did not get sticky/floating');
+
+# Cause a ConfigureRequest by setting the window’s position/size.
+my ($a, $t) = $win->rect;
+$win->rect(X11::XCB::Rect->new(x => 0, y => 0, width => $a->width, height => $a->height));
+
+does_i3_live;
+is(@{get_ws($ws)->{floating_nodes}}, 0, 'Dock client still not sticky/floating');
+
+done_testing;