diff --git a/lib/url.js b/lib/url.js
index 18cddad4276..fdf434c6c38 100644
--- a/lib/url.js
+++ b/lib/url.js
@@ -30,7 +30,7 @@ exports.format = urlFormat;
 
 // define these here so at least they only have to be
 // compiled once on the first module load.
-var protocolPattern = /^([a-z0-9]+:)/i,
+var protocolPattern = /^([a-z0-9+]+:)/i,
     portPattern = /:[0-9]+$/,
     // RFC 2396: characters reserved for delimiting URLs.
     delims = ['<', '>', '"', '`', ' ', '\r', '\n', '\t'],