--- a/browser/themes/shared/customizableui/customizeMode.inc.css
+++ b/browser/themes/shared/customizableui/customizeMode.inc.css
@@ -259,16 +259,24 @@ toolbarpaletteitem[place="toolbar"] {
 
 #customization-palette:not([hidden]) {
   margin-bottom: 25px;
 }
 
 toolbarpaletteitem[place="palette"]:-moz-focusring,
 toolbarpaletteitem[place="panel"]:-moz-focusring,
 toolbarpaletteitem[place="toolbar"]:-moz-focusring {
+  outline-width: 0;
+}
+
+toolbarpaletteitem[place="palette"]:not([mousedown="true"]):-moz-focusring,
+toolbarpaletteitem[place="panel"]:not([mousedown="true"]):-moz-focusring,
+toolbarpaletteitem[place="toolbar"]:not([mousedown="true"]):-moz-focusring {
+  /* Delay adding the focusring back until after the transform transition completes. */
+  transition: outline-width .01s linear .3s;
   outline: 1px dotted rgba(0,0,0,.5);
   outline-offset: -5px;
   -moz-outline-radius: 2.5px;
 }
 
 #wrapper-edit-controls[place="palette"] > #edit-controls > toolbarbutton,
 #wrapper-edit-controls[place="palette"] > #edit-controls > separator,
 #wrapper-zoom-controls[place="palette"] > #zoom-controls > toolbarbutton,