diff --git a/C4/Biblio.pm b/C4/Biblio.pm
index f5903f362e..78e2bad69f 100644
--- a/C4/Biblio.pm
+++ b/C4/Biblio.pm
@@ -1711,7 +1711,7 @@ sub GetMarcISBN {
 
     my @marcisbns;
     foreach my $field ( $record->field($scope) ) {
-        my $isbn = $field->as_string();
+        my $isbn = $field->subfield( 'a' );
         if ( $isbn ne "" ) {
             push @marcisbns, $isbn;
         }