diff --git a/core/src/main/java/org/keycloak/RSATokenVerifier.java b/core/src/main/java/org/keycloak/RSATokenVerifier.java
index e2f5f2b6d5a..c68da0fba21 100755
--- a/core/src/main/java/org/keycloak/RSATokenVerifier.java
+++ b/core/src/main/java/org/keycloak/RSATokenVerifier.java
@@ -35,6 +35,9 @@ public class RSATokenVerifier {
         if (user == null) {
             throw new VerificationException("Token user was null.");
         }
+        if (realmUrl == null) {
+            throw new VerificationException("Realm URL is null. Make sure to add auth-server-url to the configuration of your adapter!");
+        }
         if (!realmUrl.equals(token.getIssuer())) {
             throw new VerificationException("Token audience doesn't match domain.");
 
diff --git a/examples/cors/database-service/src/main/webapp/WEB-INF/keycloak.json b/examples/cors/database-service/src/main/webapp/WEB-INF/keycloak.json
index e93b148d350..265049f22ca 100755
--- a/examples/cors/database-service/src/main/webapp/WEB-INF/keycloak.json
+++ b/examples/cors/database-service/src/main/webapp/WEB-INF/keycloak.json
@@ -2,6 +2,7 @@
   "realm" : "cors",
   "resource" : "cors-database-service",
   "realm-public-key" : "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCrVrCuTtArbgaZzL1hvh0xtL5mc7o0NqPVnYXkLvgcwiC3BjLGw1tGEGoJaXDuSaRllobm53JBhjx33UNv+5z/UMG4kytBWxheNVKnL6GgqlNabMaFfPLPCF8kAgKnsi79NMo+n6KnSY8YeUmec/p2vjO2NjsSAVcWEQMVhJ31LwIDAQAB",
+  "auth-server-url": "http://localhost-auth:8080/auth",
   "bearer-only" : true,
   "ssl-required": "external",
   "enable-cors": true