diff --git a/src/Framework/Framework/Routing/UrlHelper.cs b/src/Framework/Framework/Routing/UrlHelper.cs
index 6783c0494a..1ec51999e0 100644
--- a/src/Framework/Framework/Routing/UrlHelper.cs
+++ b/src/Framework/Framework/Routing/UrlHelper.cs
@@ -145,7 +145,8 @@ private static bool ContainsOnlyValidUrlChars(string url)
             }
             else
             {
-                return Uri.EscapeDataString(value.ToString());
+                var strVal = value.ToString();
+                return strVal == null ? null : Uri.EscapeDataString(strVal);
             }
         }
     }