diff --git a/oidc_provider/templates/oidc_provider/check_session_iframe.html b/oidc_provider/templates/oidc_provider/check_session_iframe.html
index 445fda2..e04d5ce 100644
--- a/oidc_provider/templates/oidc_provider/check_session_iframe.html
+++ b/oidc_provider/templates/oidc_provider/check_session_iframe.html
@@ -9,6 +9,10 @@
             window.addEventListener("message", receiveMessage, false);
 
             function receiveMessage(e) {
+                if (!e.data || typeof e.data != 'string' || e.data == 'error') {
+                    return;
+                }
+
                 var status;
                 try {
                     var clientId = e.data.split(' ')[0];