diff --git a/lib/Test/MockFile.pm b/lib/Test/MockFile.pm
index bb842ed..f9aa5e4 100644
--- a/lib/Test/MockFile.pm
+++ b/lib/Test/MockFile.pm
@@ -2108,7 +2108,7 @@ sub __sysopen (*$$;$) {
 sub __opendir (*$) {
 
     # Upgrade but ignore bareword indicator
-    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[9];
+    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[0];
 
     my $mock_dir = _get_file_object( $_[1] );
 
@@ -2157,7 +2157,7 @@ sub __opendir (*$) {
 sub __readdir (*) {
 
     # Upgrade but ignore bareword indicator
-    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[9];
+    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[0];
 
     my $mocked_dir = _get_file_object( $_[0] );
 
@@ -2200,7 +2200,7 @@ sub __readdir (*) {
 sub __telldir (*) {
 
     # Upgrade but ignore bareword indicator
-    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[9];
+    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[0];
 
     my ($fh) = @_;
     my $mocked_dir = _get_file_object($fh);
@@ -2227,7 +2227,7 @@ sub __telldir (*) {
 sub __rewinddir (*) {
 
     # Upgrade but ignore bareword indicator
-    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[9];
+    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[0];
 
     my ($fh) = @_;
     my $mocked_dir = _get_file_object($fh);
@@ -2255,7 +2255,7 @@ sub __rewinddir (*) {
 sub __seekdir (*$) {
 
     # Upgrade but ignore bareword indicator
-    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[9];
+    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[0];
 
     my ( $fh, $goto ) = @_;
     my $mocked_dir = _get_file_object($fh);
@@ -2276,13 +2276,14 @@ sub __seekdir (*$) {
         confess("seekdir called on a closed dirhandle");
     }
 
-    return $obj->{'tell'} = $goto;
+    $obj->{'tell'} = $goto;
+    return 1;
 }
 
 sub __closedir (*) {
 
     # Upgrade but ignore bareword indicator
-    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[9];
+    ( undef, @_ ) = _upgrade_barewords(@_) if defined $_[0] && !ref $_[0];
 
     my ($fh) = @_;
     my $mocked_dir = _get_file_object($fh);
diff --git a/t/opendir.t b/t/opendir.t
index ebe9cf9..f712bff 100644
--- a/t/opendir.t
+++ b/t/opendir.t
@@ -145,5 +145,33 @@ is(
     closedir($dh);
 }
 
+note "-------------- BAREWORD GUARD REGRESSION --------------";
+# Regression: the bareword upgrade guard was checking $_[9] (always undef
+# for 1-2 arg dir functions) instead of $_[0]. This meant _upgrade_barewords
+# ran unconditionally, even for reference filehandles.
+# Also: seekdir must return 1 (like CORE::seekdir), not the seek position.
+{
+    my $mock_dir  = Test::MockFile->dir('/guardtest');
+    my $mock_file = Test::MockFile->file( '/guardtest/aaa', 'data' );
+
+    is( opendir( my $dh, '/guardtest' ), 1, "opendir with ref filehandle works" );
+
+    is( scalar readdir($dh), ".",   "readdir with ref fh reads ." );
+    is( scalar readdir($dh), "..",  "readdir with ref fh reads .." );
+    is( telldir($dh),        2,     "telldir with ref fh returns correct position" );
+    is( scalar readdir($dh), "aaa", "readdir with ref fh reads aaa" );
+
+    is( rewinddir($dh), 1, "rewinddir with ref fh returns 1" );
+    is( telldir($dh),   0, "telldir after rewinddir is 0" );
+
+    # seekdir's return value is not reliably testable across Perl versions
+    # with CORE::GLOBAL overrides — test the effect instead.
+    seekdir( $dh, 2 );
+    is( telldir($dh),      2,       "telldir is 2 after seekdir(2)" );
+    is( [ readdir($dh) ],  ["aaa"], "readdir after seekdir(2) returns remaining entries" );
+
+    is( closedir($dh), 1, "closedir with ref fh returns 1" );
+}
+
 done_testing();
 exit;