diff --git a/toolkit/themes/pinstripe/mozapps/extensions/extensions.css b/toolkit/themes/pinstripe/mozapps/extensions/extensions.css
index a0f3ae9a4a9d..58386363597b 100644
--- a/toolkit/themes/pinstripe/mozapps/extensions/extensions.css
+++ b/toolkit/themes/pinstripe/mozapps/extensions/extensions.css
@@ -4,12 +4,14 @@
 }
 
 #resizerBox {
-margin-top: -12px;
+  margin-top: -12px;
+  visibility: hidden;
 }
 
-#resizerBox resizer {
+#resizerBox > resizer {
   height: 10px;
   max-height: 10px;
+  visibility: visible;
 }
 
 /* Command Bar */
diff --git a/toolkit/themes/winstripe/mozapps/extensions/extensions.css b/toolkit/themes/winstripe/mozapps/extensions/extensions.css
index 13583109c6ec..717c3ea5fe1a 100644
--- a/toolkit/themes/winstripe/mozapps/extensions/extensions.css
+++ b/toolkit/themes/winstripe/mozapps/extensions/extensions.css
@@ -12,12 +12,14 @@
 }
 
 #resizerBox {
-margin-top: -12px;
+  margin-top: -12px;
+  visibility: hidden;
 }
 
-#resizerBox resizer {
+#resizerBox > resizer {
   height: 10px;
   max-height: 10px;
+  visibility: visible;
 }
 
 /* Command Bar */