diff --git a/oauth3.core.js b/oauth3.core.js
index d48d8be..e268388 100644
--- a/oauth3.core.js
+++ b/oauth3.core.js
@@ -1300,10 +1300,10 @@
         // The username may have a single @, the provider may not
         // user@thing.com@whatever.com -> user@thing.com, whatever.com
         issuer = parts.pop();
-        subject = parts.join('');
+        subject = parts.join('@');
       } else {
         //subject = '';
-        issuer = parts.join('');
+        issuer = parts.join('@');
       }
 
       return { subject: subject, issuer: issuer };