diff --git a/lib/httpclient/util.rb b/lib/httpclient/util.rb
index 6ff3801..8657949 100644
--- a/lib/httpclient/util.rb
+++ b/lib/httpclient/util.rb
@@ -64,7 +64,7 @@ class AddressableURI < Addressable::URI
         # Overwrites the original definition just for one line...
         def authority
           self.host && @authority ||= (begin
-            authority = ""
+            authority = +""
             if self.userinfo != nil
               authority << "#{self.userinfo}@"
             end