diff --git magnolia-core/src/main/java/info/magnolia/cms/security/MgnlUserManager.java magnolia-core/src/main/java/info/magnolia/cms/security/MgnlUserManager.java
index 317b3e0..473003d 100644
--- magnolia-core/src/main/java/info/magnolia/cms/security/MgnlUserManager.java
+++ magnolia-core/src/main/java/info/magnolia/cms/security/MgnlUserManager.java
@@ -233,6 +233,11 @@ public class MgnlUserManager extends RepositoryBackedSecurityManager implements
      */
     @Override
     public User getUser(final String name) {
+        if (StringUtils.isBlank(name)) {
+            log.debug("name not set.");
+            return null;
+        }
+
         try {
             return MgnlContext.doInSystemContext(new JCRSessionOp<User>(getRepositoryName()) {
                 @Override