diff --git a/modules/Bio/EnsEMBL/Feature.pm b/modules/Bio/EnsEMBL/Feature.pm
index 5b4c232dbc90b6f26910d1f9d4a080d09a30b042..230c9ee2ed1121025bff02e73f2bf675f227b5dd 100644
--- a/modules/Bio/EnsEMBL/Feature.pm
+++ b/modules/Bio/EnsEMBL/Feature.pm
@@ -380,7 +380,7 @@ sub slice {
 
     $self->{'slice'} = $slice;
   } elsif ( @_ > 1 ) {
-    undef $self->{'slice'};
+    delete($self->{'slice'});
   }
 
   return $self->{'slice'};