diff --git a/src/umbraco.cms/helpers/url.cs b/src/umbraco.cms/helpers/url.cs
index e32b0333f4..0e344412f7 100644
--- a/src/umbraco.cms/helpers/url.cs
+++ b/src/umbraco.cms/helpers/url.cs
@@ -38,6 +38,9 @@ namespace umbraco.cms.helpers
                 return false;
             }
 
+            if (url.StartsWith("//"))
+                return false;
+
             Uri requestUri;
             if (Uri.TryCreate(url, UriKind.RelativeOrAbsolute, out requestUri))
             {