diff --git a/lib/passport-wsfed-saml2/wsfederation.js b/lib/passport-wsfed-saml2/wsfederation.js
index f7b3b70..8af9ced 100644
--- a/lib/passport-wsfed-saml2/wsfederation.js
+++ b/lib/passport-wsfed-saml2/wsfederation.js
@@ -27,7 +27,9 @@ WsFederation.prototype = {
       query.wreply = this.wreply;
     }
 
-    return this.identityProviderUrl + '?' + qs.encode(query);
+    var conjunction = (this.identityProviderUrl.indexOf('?') === -1) ? '?' : '&';
+
+    return this.identityProviderUrl + conjunction + qs.encode(query);
   },
 
   extractToken: function(req) {