diff --git a/django/contrib/admin/views/decorators.py b/django/contrib/admin/views/decorators.py
index cedb1f9cfd4..3039daadb11 100644
--- a/django/contrib/admin/views/decorators.py
+++ b/django/contrib/admin/views/decorators.py
@@ -85,7 +85,13 @@ def staff_member_required(view_func):
             if '@' in username:
                 # Mistakenly entered e-mail address instead of username? Look it up.
                 try:
-                    user = User.objects.get(email=username)
+                    users = list(User.objects.filter(email=username))
+                    if len(users) == 1:
+                        user = users[0]
+                    else:
+                        # Either we cannot find the user, or if more than 1 
+                        # we cannot guess which user is the correct one.
+                        raise User.DoesNotExist()                        
                 except User.DoesNotExist:
                     message = _("Usernames cannot contain the '@' character.")
                 else: