diff --git a/web/src/main/java/org/springframework/security/web/authentication/rememberme/AbstractRememberMeServices.java b/web/src/main/java/org/springframework/security/web/authentication/rememberme/AbstractRememberMeServices.java
index 5dd1d3745d..2087c06924 100644
--- a/web/src/main/java/org/springframework/security/web/authentication/rememberme/AbstractRememberMeServices.java
+++ b/web/src/main/java/org/springframework/security/web/authentication/rememberme/AbstractRememberMeServices.java
@@ -81,7 +81,7 @@ public abstract class AbstractRememberMeServices implements RememberMeServices,
     }
 
     public void afterPropertiesSet() throws Exception {
-        Assert.hasLength(key);
+        Assert.hasLength(key, "key cannot be empty or null");
         Assert.notNull(userDetailsService, "A UserDetailsService is required");
     }