diff --git a/static/client/register/js/register.js b/static/client/register/js/register.js
index 38408f731f9efd079d5e544392c9a95d4c843e78..b62763a2934de2a26101b55372def558f29f8c39 100644
--- a/static/client/register/js/register.js
+++ b/static/client/register/js/register.js
@@ -23,6 +23,7 @@ var setupCaptcha = function() {
         var public_key = window.matrixRegistrationConfig.recaptcha_public_key;
         if (public_key === undefined) {
             console.error("No public key defined for captcha!");
+            setFeedbackString("Misconfigured captcha for server. Contact server admin.");
             return;
         }
         Recaptcha.create(public_key,