diff --git a/src/components/views/auth/InteractiveAuthEntryComponents.js b/src/components/views/auth/InteractiveAuthEntryComponents.js
index f7bba5ba4a..eaff2d0543 100644
--- a/src/components/views/auth/InteractiveAuthEntryComponents.js
+++ b/src/components/views/auth/InteractiveAuthEntryComponents.js
@@ -190,14 +190,21 @@ export const RecaptchaAuthEntry = createReactClass({
             return <Loader />;
         }
 
+        let errorText = this.props.errorText;
+
         const CaptchaForm = sdk.getComponent("views.auth.CaptchaForm");
-        const sitePublicKey = this.props.stageParams.public_key;
+        let sitePublicKey;
+        if (!this.props.stageParams || !this.props.stageParams.public_key) {
+            errorText = _t("Missing captcha public key - check your server configuration");
+        } else {
+            sitePublicKey = this.props.stageParams.public_key;
+        }
 
         let errorSection;
-        if (this.props.errorText) {
+        if (errorText) {
             errorSection = (
                 <div className="error" role="alert">
-                    { this.props.errorText }
+                    { errorText }
                 </div>
             );
         }
diff --git a/src/i18n/strings/en_EN.json b/src/i18n/strings/en_EN.json
index b303b7a94d..f1ff2982fd 100644
--- a/src/i18n/strings/en_EN.json
+++ b/src/i18n/strings/en_EN.json
@@ -1478,6 +1478,7 @@
     "You can use the custom server options to sign into other Matrix servers by specifying a different homeserver URL. This allows you to use this app with an existing Matrix account on a different homeserver.": "You can use the custom server options to sign into other Matrix servers by specifying a different homeserver URL. This allows you to use this app with an existing Matrix account on a different homeserver.",
     "You can also set a custom identity server, but you won't be able to invite users by email address, or be invited by email address yourself.": "You can also set a custom identity server, but you won't be able to invite users by email address, or be invited by email address yourself.",
     "To continue, please enter your password.": "To continue, please enter your password.",
+    "Missing captcha public key - check your server configuration": "Missing captcha public key - check your server configuration",
     "Please review and accept all of the homeserver's policies": "Please review and accept all of the homeserver's policies",
     "Please review and accept the policies of this homeserver:": "Please review and accept the policies of this homeserver:",
     "An email has been sent to %(emailAddress)s": "An email has been sent to %(emailAddress)s",