diff --git a/src/bin/build-keycloak-theme/generateFtl/register.ftl b/src/bin/build-keycloak-theme/generateFtl/register.ftl
index 7635e5d2..5fe3d016 100644
--- a/src/bin/build-keycloak-theme/generateFtl/register.ftl
+++ b/src/bin/build-keycloak-theme/generateFtl/register.ftl
@@ -41,6 +41,6 @@
         return false;
 
     })(),
-    "recaptchaSiteKey": "${recaptchaSiteKey}"
+    "recaptchaSiteKey": "${recaptchaSiteKey!''}" || undefined
 }
 </script>
\ No newline at end of file
diff --git a/src/lib/kcContext.ts b/src/lib/kcContext.ts
index 22a873ac..b8ff8a6e 100644
--- a/src/lib/kcContext.ts
+++ b/src/lib/kcContext.ts
@@ -113,7 +113,8 @@ export declare namespace KcContext {
         };
         passwordRequired: boolean;
         recaptchaRequired: boolean;
-        recaptchaSiteKey: string;
+        /** undefined if !recaptchaRequired */
+        recaptchaSiteKey?: string;
     };
 
 }