LDAP cresentials with sAMAccountName including uppercase letter does not work with Global Security

With LDAP auth, the sAMAccountName containing uppercase case letters does not work with Global Security. For example, user ID "testuser" can be specified in the Global Security as expected. However, user ID "TEstuser" does not work as expected with the Global Security specified as TEstuser. In the Jenkis home dir there is a dir for either users/testuser/config.xml and users/TEstuser/config.xml. It just doesn't work with the ID containing uppercase letters.