diff --git a/modules/Bio/EnsEMBL/Variation/Utils/VEP.pm b/modules/Bio/EnsEMBL/Variation/Utils/VEP.pm
index 7fbe57d379..3ebf097ffa 100644
--- a/modules/Bio/EnsEMBL/Variation/Utils/VEP.pm
+++ b/modules/Bio/EnsEMBL/Variation/Utils/VEP.pm
@@ -950,7 +950,7 @@ sub convert_to_vcf {
             # default to N in case we can't get it
             my $prev_base = 'N';
             
-            if(defined($vf->slice)) {
+            if(defined($vf->slice) && UNIVERSAL::isa($vf->slice,'can')) {
                 my $slice = $vf->slice->sub_Slice($vf->start - 1, $vf->start - 1);
                 $prev_base = $slice->seq if defined($slice);
             }