diff --git a/src/plone/api/env.py b/src/plone/api/env.py
index fb18122..ce8652c 100644
--- a/src/plone/api/env.py
+++ b/src/plone/api/env.py
@@ -39,7 +39,10 @@ def adopt_user(username=None, user=None):
     acl_users = portal.get().acl_users
     unwrapped = acl_users.getUser(username)
     if unwrapped is None:
-        raise UserNotFoundError
+        acl_users = portal.get().unrestrictedTraverse('/').acl_users
+        unwrapped = acl_users.getUser(username)
+        if unwrapped is None:
+            raise UserNotFoundError
 
     # ZopeSecurityPolicy appears to strongly expect the user object to
     # be Acquisition-wrapped in the acl_users from which it was taken.