diff --git a/modules/Bio/EnsEMBL/Slice.pm b/modules/Bio/EnsEMBL/Slice.pm
index fb4ce106fe686afcde1c066edb31050b5a36b1dc..0c7425bd9cb76f0e2a665eecdf5a764eaf2b2d47 100644
--- a/modules/Bio/EnsEMBL/Slice.pm
+++ b/modules/Bio/EnsEMBL/Slice.pm
@@ -153,11 +153,11 @@ sub new {
     throw('SEQ_REGION_LENGTH must be > 0');
   }
 
-  if ( defined($seq) && length($seq) != ( $end - $start + 1 ) ) {
-    throw(   'SEQ must be the same length as the defined LENGTH not '
-           . length($seq)
-           . ' compared to '
-           . ( $end - $start + 1 ) );
+  if ( defined($seq) && CORE::length($seq) != ( $end - $start + 1 ) ) {
+    throw('SEQ must be the same length as the defined LENGTH not '
+        . CORE::length($seq)
+        . ' compared to '
+        . ( $end - $start + 1 ) );
   }
 
   if(defined($coord_system)) {