diff --git a/bin/run-perltidy.pl b/bin/run-perltidy.pl
index 28c28c1ab..e5d6a4215 100755
--- a/bin/run-perltidy.pl
+++ b/bin/run-perltidy.pl
@@ -67,7 +67,7 @@ =head1 OPTIONS
 exit $err                                                if $err;
 die "The -pro option is not supported by this script.\n" if defined $options{profile};
 
-unshift(@args, '-bext=/') unless defined $options{'backup-file-extension'};
+unshift(@args, '-bext=/tidybak') unless defined $options{'backup-file-extension'};
 
 if (@files) {
 	for (@files) {