diff --git a/chrome.manifest b/chrome.manifest
index c9dbf040..95180015 100644
--- a/chrome.manifest
+++ b/chrome.manifest
@@ -45,6 +45,7 @@ override chrome://treestyletab/skin/platform-styled.css	chrome://treestyletab/sk
 override chrome://treestyletab/skin/square/platform.css	chrome://treestyletab/skin/square/Darwin.css	os=Darwin
 override chrome://treestyletab/skin/square/platform.css	chrome://treestyletab/skin/square/Linux.css	os=Linux
 override chrome://treestyletab/skin/square/platform.css	chrome://treestyletab/skin/dummy.css	os=WINNT
+override chrome://treestyletab/skin/square/disable-closebox-bg.css	chrome://treestyletab/skin/dummy.css	os=Linux appversion>=31.0a1
 
 override chrome://treestyletab/skin/metal/platform.css	chrome://treestyletab/skin/metal/Darwin.css	os=Darwin
 override chrome://treestyletab/skin/metal/platform.css	chrome://treestyletab/skin/dummy.css	os=WINNT
diff --git a/skin/classic/treestyletab/square/base.css b/skin/classic/treestyletab/square/base.css
index 6cc3e0da..a88787f5 100644
--- a/skin/classic/treestyletab/square/base.css
+++ b/skin/classic/treestyletab/square/base.css
@@ -1,3 +1,5 @@
+@import url("./disable-closebox-bg.css");
+
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 
 /* Default style */
@@ -218,15 +220,8 @@
 .tabbrowser-tabs:not([treestyletab-tabbar-position="top"])
   .tabbrowser-tab
   .tab-close-button {
-	height: auto;
 	margin: 0 !important;
 	padding: 0 !important;
-	background: transparent;
-}
-.tabbrowser-tabs:not([treestyletab-tabbar-position="top"])
-  .tabbrowser-tab[selected="true"]
-  .tab-close-button {
-	background: transparent;
 }
 
 .tabbrowser-tabs[treestyletab-mode="vertical"]
diff --git a/skin/classic/treestyletab/square/disable-closebox-bg.css b/skin/classic/treestyletab/square/disable-closebox-bg.css
new file mode 100644
index 00000000..0b75ed87
--- /dev/null
+++ b/skin/classic/treestyletab/square/disable-closebox-bg.css
@@ -0,0 +1,20 @@
+@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
+
+/**
+ * Disable background images for closebox in tabs.
+ * This must be activated on:
+ *  - WINNT, any version
+ *  - OS X, any version
+ *  - Linux, Firefox 30 or older
+ * See: https://bugzilla.mozilla.org/show_bug.cgi?id=879921
+ */
+
+.tabbrowser-tabs:not([treestyletab-tabbar-position="top"])
+  .tabbrowser-tab
+  .tab-close-button,
+.tabbrowser-tabs:not([treestyletab-tabbar-position="top"])
+  .tabbrowser-tab[selected="true"]
+  .tab-close-button {
+	height: auto;
+	background: transparent;
+}