diff --git a/system/src/Grav/Common/Assets.php b/system/src/Grav/Common/Assets.php
index e08ec3425..64fd32077 100644
--- a/system/src/Grav/Common/Assets.php
+++ b/system/src/Grav/Common/Assets.php
@@ -34,7 +34,7 @@ class Assets
     const JS_REGEX = '/.\.js$/i';
 
     /** @const Regex to match CSS urls */
-    const CSS_URL_REGEX = '{url\([\'\"]?((?!http|//).*?)[\'\"]?\)}';
+    const CSS_URL_REGEX = '{url\(([\'\"]?)(.*?)\1\)}';
 
     /** @const Regex to match CSS sourcemap comments */
     const CSS_SOURCEMAP_REGEX = '{\/\*# (.*) \*\/}';
@@ -1149,13 +1149,18 @@ class Assets
         // Then replace the old url with the new one
         $file = preg_replace_callback(self::CSS_URL_REGEX, function ($matches) use ($relative_path) {
 
-            $old_url = $matches[1];
+            $old_url = $matches[2];
 
             // ensure this is not a data url
             if (strpos($old_url, 'data:') === 0) {
                 return $matches[0];
             }
 
+            // ensure this is not a remote url
+            if ($this->isRemoteLink($old_url)) {
+                return $matches[0];
+            }
+
             $new_url = $this->base_url . ltrim(Utils::normalizePath($relative_path . '/' . $old_url), '/');
 
             return str_replace($old_url, $new_url, $matches[0]);