diff --git a/lib/browser/PayPro.js b/lib/browser/PayPro.js
index f27b879..781a6ab 100644
--- a/lib/browser/PayPro.js
+++ b/lib/browser/PayPro.js
@@ -119,7 +119,7 @@ PayPro.prototype.x509Verify = function(key) {
     // Create a To-Be-Signed Certificate to verify using asn1.js:
     // Fails at Issuer:
     var tbs = rfc3280.TBSCertificate.encode(c.tbsCertificate, 'der');
-    jsrsaSig.updateHex(tbs);
+    jsrsaSig.updateHex(tbs.toString('hex'));
 
     return jsrsaSig.verify(sig);
   });