--- a/account.pm	Tue Dec 13 21:45:06 2011 +0100
+++ b/account.pm	Tue Dec 13 21:50:43 2011 +0100
@@ -344,7 +344,11 @@
 
             }
 
-            $e->replace( (AT_ACLGROUPS) => $ag );
+            if ($ag) {
+                $e->replace( (AT_ACLGROUPS) => $ag );
+            } else {
+                $e->delete( AT_ACLGROUPS );
+            }
             $modified++;
         }