diff --git a/modules/Bio/EnsEMBL/Archive/VersionedSeq.pm b/modules/Bio/EnsEMBL/Archive/VersionedSeq.pm
index 36c3a5253f2773a63a88a7548d6686eecdba4a35..896760bd9f818a0b249bc3d1f1137b96a437aa9f 100644
--- a/modules/Bio/EnsEMBL/Archive/VersionedSeq.pm
+++ b/modules/Bio/EnsEMBL/Archive/VersionedSeq.pm
@@ -59,6 +59,7 @@ use strict;
 # (inherits for methods like throw and rearrange)
 
 use Bio::Root::RootI;
+use Bio::PrimarySeqI;
 
 @ISA = qw(Bio::Root::RootI Bio::PrimarySeqI);