diff --git a/app/dialogs/about-dialog.c b/app/dialogs/about-dialog.c
index e7ff0a7b38..7a9f42aa7c 100644
--- a/app/dialogs/about-dialog.c
+++ b/app/dialogs/about-dialog.c
@@ -192,6 +192,9 @@ about_dialog_create (Gimp           *gimp,
       g_list_free (children);
     }
 
+  gtk_style_context_add_class (gtk_widget_get_style_context (dialog.dialog),
+                               "gimp-about-dialog");
+
   return dialog.dialog;
 }
 
diff --git a/themes/Default/common.css b/themes/Default/common.css
index 35cb82acee..5487a54fd0 100644
--- a/themes/Default/common.css
+++ b/themes/Default/common.css
@@ -75,6 +75,12 @@ GimpDisplayShell, GimpDock, .dialog-action-box, .dialog-vbox {
   color: @dimmed-fg-color;
 }
 
+/* Prevent system theme leak that adds a border around
+ * the toolbox Wilber */
+GimpDock frame border {
+  background-image: none;
+}
+
 /* Foreground color for the big Wilber in the empty image window.
  * Again, background-color and background here are ignored.
  */
@@ -82,6 +88,12 @@ GimpDisplayShell, GimpDock, .dialog-action-box, .dialog-vbox {
   color: @dimmed-fg-color;
 }
 
+/* Prevent system theme leak that affects the color of the
+ * main canvas and some widget containers  */
+stack {
+  background-image: none;
+}
+
 /* GtkTextView */
 textview text, textview {
   background-color: @extreme-bg-color;
@@ -280,8 +292,13 @@ scrolledwindow
 
 /* Removes black border around scrolled windows */
 scrolledwindow viewport grid, scrolledwindow viewport box {
-   border-radius: 1px;
-   border: 0px solid @bg-color;
+  border-radius: 1px;
+  border: 0px solid @bg-color;
+}
+
+/* Defining background color for About Dialog credits box */
+.gimp-about-dialog box box stack scrolledwindow viewport grid {
+  background-color: @extreme-bg-color;
 }
 
 GimpRuler {