diff --git a/lib/auth.js b/lib/auth.js
index 272443e26..66d3f5ce0 100644
--- a/lib/auth.js
+++ b/lib/auth.js
@@ -32,7 +32,7 @@ var digest = {};
 
 digest.parse_header = function(header) {
   var challenge = {},
-      matches   = header.match(/([a-z0-9_-]+)="?([a-z0-9=\/\.@\s-\+)()]+)"?/gi);
+      matches   = header.match(/([a-z0-9_-]+)="?([a-z0-9_=\/\.@\s-\+)()]+)"?/gi);
 
   for (var i = 0, l = matches.length; i < l; i++) {
     var parts = matches[i].split('='),