diff --git a/src/shell-window-tracker.c b/src/shell-window-tracker.c
index c8b473d9a..bc00518ea 100644
--- a/src/shell-window-tracker.c
+++ b/src/shell-window-tracker.c
@@ -146,9 +146,13 @@ get_app_from_window_wmclass (MetaWindow  *window)
   const char *wm_class;
   const char *wm_instance;
   const char *sandbox_id;
+  g_autofree char *app_prefix = NULL;
 
   appsys = shell_app_system_get_default ();
+
   sandbox_id = meta_window_get_sandboxed_app_id (window);
+  if (sandbox_id)
+    app_prefix = g_strdup_printf ("%s.", sandbox_id);
 
   /* Notes on the heuristics used here:
      much of the complexity here comes from the desire to support
@@ -188,23 +192,23 @@ get_app_from_window_wmclass (MetaWindow  *window)
   /* first try a match from WM_CLASS (instance part) to StartupWMClass */
   wm_instance = meta_window_get_wm_class_instance (window);
   app = shell_app_system_lookup_startup_wmclass (appsys, wm_instance);
-  if (app != NULL && check_app_id_prefix (app, sandbox_id))
+  if (app != NULL && check_app_id_prefix (app, app_prefix))
     return g_object_ref (app);
 
   /* then try a match from WM_CLASS to StartupWMClass */
   wm_class = meta_window_get_wm_class (window);
   app = shell_app_system_lookup_startup_wmclass (appsys, wm_class);
-  if (app != NULL && check_app_id_prefix (app, sandbox_id))
+  if (app != NULL && check_app_id_prefix (app, app_prefix))
     return g_object_ref (app);
 
   /* then try a match from WM_CLASS (instance part) to .desktop */
   app = shell_app_system_lookup_desktop_wmclass (appsys, wm_instance);
-  if (app != NULL && check_app_id_prefix (app, sandbox_id))
+  if (app != NULL && check_app_id_prefix (app, app_prefix))
     return g_object_ref (app);
 
   /* finally, try a match from WM_CLASS to .desktop */
   app = shell_app_system_lookup_desktop_wmclass (appsys, wm_class);
-  if (app != NULL && check_app_id_prefix (app, sandbox_id))
+  if (app != NULL && check_app_id_prefix (app, app_prefix))
     return g_object_ref (app);
 
   return NULL;