Need idea to get rid of delegation warning for Lower

In the App.Formula I have follow line setup. The delegation warning is shown for Lower(UserAccount):

nfCurrentUser = LookUp(Users,Lower(UserAccount)=Lower(nfCurrentUser.Email));

There are only 500 users in "Users" list. So I think we can safely ignore the delegation warning. But it is quite annoying everytime I open the App Studio. Is there any work around to get rid of warning? I cannot change the UserAccount value because it is directly copy from AAD. The value in AAD has upper and lower case in their email addresses.