diff --git a/menu_icons.module b/menu_icons.module
index addefc0..b6fdf46 100755
--- a/menu_icons.module
+++ b/menu_icons.module
@@ -515,6 +515,8 @@ function menu_icons_css_generate() {
 
       if ($absolute) {
         $image_url = file_create_url($image_path);
+        // Convert the image into a protocol-relative URL.
+        $image_url = preg_replace('/^https?:/', '', $image_url);
       }
       else {
         $wrapper = file_stream_wrapper_get_instance_by_scheme(file_uri_scheme($image_path));