diff --git a/modules/Bio/EnsEMBL/RepeatMaskedSlice.pm b/modules/Bio/EnsEMBL/RepeatMaskedSlice.pm
index e75fac1296e80df2c4aede47338bb0b84265625d..445d67d706e3b917fa64653441c671b2f6a3d6c7 100644
--- a/modules/Bio/EnsEMBL/RepeatMaskedSlice.pm
+++ b/modules/Bio/EnsEMBL/RepeatMaskedSlice.pm
@@ -263,8 +263,8 @@ sub subseq {
     
     my $seq_region_slice = $self->seq_region_Slice();
     # The blocksize can be defined on the top of this module.
-    my $block_min = ($self->start()-1) >> $BLOCK_PWR;
-    my $block_max = ($self->end()-1) >> $BLOCK_PWR;
+    my $block_min = ($subsequence_slice->start()-1) >> $BLOCK_PWR;
+    my $block_max = ($subsequence_slice->end()-1) >> $BLOCK_PWR;
     
     my $sub_start = ($block_min << $BLOCK_PWR)+1;
     my $sub_end = ($block_max+1)<<$BLOCK_PWR;