diff --git a/i3bar/src/xcb.c b/i3bar/src/xcb.c
index 06cff98de..ecb41a603 100644
--- a/i3bar/src/xcb.c
+++ b/i3bar/src/xcb.c
@@ -685,19 +685,6 @@ static void handle_visibility_notify(xcb_visibility_notify_event_t *event) {
     }
 }
 
-static int strcasecmp_nullable(const char *a, const char *b) {
-    if (a == b) {
-        return 0;
-    }
-    if (a == NULL) {
-        return -1;
-    }
-    if (b == NULL) {
-        return 1;
-    }
-    return strcasecmp(a, b);
-}
-
 /*
  * Comparison function to sort trayclients in ascending alphanumeric order
  * according to their class.
@@ -1816,6 +1803,8 @@ void reconfig_windows(bool redraw_bars) {
                                                                       bar_height);
 
             /* Set the WM_CLASS and WM_NAME (we don't need UTF-8) atoms */
+            char *class;
+            int len = sasprintf(&class, "%s%ci3bar%c", config.bar_id, 0, 0);
             xcb_void_cookie_t class_cookie;
             class_cookie = xcb_change_property(xcb_connection,
                                                XCB_PROP_MODE_REPLACE,
@@ -1823,8 +1812,8 @@ void reconfig_windows(bool redraw_bars) {
                                                XCB_ATOM_WM_CLASS,
                                                XCB_ATOM_STRING,
                                                8,
-                                               (strlen("i3bar") + 1) * 2,
-                                               "i3bar\0i3bar\0");
+                                               len,
+                                               class);
 
             char *name;
             sasprintf(&name, "i3bar for output %s", walk->name);
diff --git a/include/libi3.h b/include/libi3.h
index 15d1bc76c..d9c89ddd5 100644
--- a/include/libi3.h
+++ b/include/libi3.h
@@ -181,6 +181,12 @@ ssize_t writeall_nonblock(int fd, const void *buf, size_t count);
  */
 ssize_t swrite(int fd, const void *buf, size_t count);
 
+/**
+ * Like strcasecmp but considers the case where either string is NULL.
+ *
+ */
+int strcasecmp_nullable(const char *a, const char *b);
+
 /**
  * Build an i3String from an UTF-8 encoded string.
  * Returns the newly-allocated i3String.
diff --git a/libi3/safewrappers.c b/libi3/safewrappers.c
index 1802b327e..fdea636ee 100644
--- a/libi3/safewrappers.c
+++ b/libi3/safewrappers.c
@@ -110,3 +110,20 @@ ssize_t swrite(int fd, const void *buf, size_t count) {
     else
         return n;
 }
+
+/*
+ * Like strcasecmp but considers the case where either string is NULL.
+ *
+ */
+int strcasecmp_nullable(const char *a, const char *b) {
+    if (a == b) {
+        return 0;
+    }
+    if (a == NULL) {
+        return -1;
+    }
+    if (b == NULL) {
+        return 1;
+    }
+    return strcasecmp(a, b);
+}
diff --git a/src/con.c b/src/con.c
index ba0eaa3cc..08bb7e4ed 100644
--- a/src/con.c
+++ b/src/con.c
@@ -132,6 +132,30 @@ static void _con_attach(Con *con, Con *parent, Con *previous, bool ignore_focus)
         goto add_to_focus_head;
     }
 
+    if (parent->type == CT_DOCKAREA) {
+        /* Insert dock client, sorting alphanumerically by class and then
+         * instance name. This makes dock client order deterministic. As a side
+         * effect, bars without a custom bar id will be sorted according to
+         * their declaration order in the config file. See #3491. */
+        current = NULL;
+        TAILQ_FOREACH (loop, nodes_head, nodes) {
+            int result = strcasecmp_nullable(con->window->class_class, loop->window->class_class);
+            if (result == 0) {
+                result = strcasecmp_nullable(con->window->class_instance, loop->window->class_instance);
+            }
+            if (result < 0) {
+                current = loop;
+                break;
+            }
+        }
+        if (current) {
+            TAILQ_INSERT_BEFORE(loop, con, nodes);
+        } else {
+            TAILQ_INSERT_TAIL(nodes_head, con, nodes);
+        }
+        goto add_to_focus_head;
+    }
+
     if (con->type == CT_FLOATING_CON) {
         DLOG("Inserting into floating containers\n");
         TAILQ_INSERT_TAIL(&(parent->floating_head), con, floating_windows);
diff --git a/src/handlers.c b/src/handlers.c
index ed3f6c3ed..d6d6e20bc 100644
--- a/src/handlers.c
+++ b/src/handlers.c
@@ -1148,9 +1148,7 @@ static bool handle_strut_partial_change(Con *con, xcb_get_property_reply_t *prop
 
     /* attach the dock to the dock area */
     con_detach(con);
-    con->parent = dockarea;
-    TAILQ_INSERT_HEAD(&(dockarea->focus_head), con, focused);
-    TAILQ_INSERT_HEAD(&(dockarea->nodes_head), con, nodes);
+    con_attach(con, dockarea, true);
 
     tree_render();