diff --git a/modules/Bio/EnsEMBL/OntologyXref.pm b/modules/Bio/EnsEMBL/OntologyXref.pm
index 5ca21775b175f0d01422d6518972c771fe78ad50..f0c0448c1992a5447116ef96ddf1ab298cb4fc0a 100644
--- a/modules/Bio/EnsEMBL/OntologyXref.pm
+++ b/modules/Bio/EnsEMBL/OntologyXref.pm
@@ -63,10 +63,9 @@ identifier but with different evidence tags.  For this reason a single
 
 package Bio::EnsEMBL::OntologyXref;
 
-use vars qw(@ISA);
 use strict;
 
-@ISA = qw( Bio::EnsEMBL::DBEntry );
+use parent qw( Bio::EnsEMBL::DBEntry );
 
 =head2 add_linkage_type