diff --git a/pre_commit_hooks/check_shebang_scripts_are_executable.py b/pre_commit_hooks/check_shebang_scripts_are_executable.py
index 937425b0..07c43fad 100644
--- a/pre_commit_hooks/check_shebang_scripts_are_executable.py
+++ b/pre_commit_hooks/check_shebang_scripts_are_executable.py
@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import argparse
+import os
 import shlex
 import sys
 from collections.abc import Sequence
@@ -9,13 +10,34 @@
 from pre_commit_hooks.check_executables_have_shebangs import EXECUTABLE_VALUES
 from pre_commit_hooks.check_executables_have_shebangs import git_ls_files
 from pre_commit_hooks.check_executables_have_shebangs import has_shebang
+from pre_commit_hooks.util import CalledProcessError
+from pre_commit_hooks.util import cmd_output
 
 
 def check_shebangs(paths: list[str]) -> int:
-    # Cannot optimize on non-executability here if we intend this check to
-    # work on win32 -- and that's where problems caused by non-executability
-    # (elsewhere) are most likely to arise from.
-    return _check_git_filemode(paths)
+    # Use the index when available: its executable bits are authoritative for
+    # staged files, especially on platforms that cannot track file modes.
+    try:
+        return _check_git_filemode(paths)
+    except CalledProcessError:
+        # Do not hide an unrelated Git failure in a working tree.
+        if cmd_output(
+                'git', 'rev-parse', '--is-inside-work-tree', retcode=None,
+        ).strip() == 'true':
+            raise
+        if sys.platform == 'win32':
+            # Windows cannot reliably determine Unix executable bits.
+            raise
+        return _check_fs_filemode(paths)
+
+
+def _check_fs_filemode(paths: Sequence[str]) -> int:
+    found = False
+    for path in paths:
+        if not os.access(path, os.X_OK) and has_shebang(path):
+            _message(path)
+            found = True
+    return int(found)
 
 
 def _check_git_filemode(paths: Sequence[str]) -> int:
diff --git a/tests/check_shebang_scripts_are_executable_test.py b/tests/check_shebang_scripts_are_executable_test.py
index e4bd07ca..a3bc24d9 100644
--- a/tests/check_shebang_scripts_are_executable_test.py
+++ b/tests/check_shebang_scripts_are_executable_test.py
@@ -1,9 +1,12 @@
 from __future__ import annotations
 
 import os
+import sys
+from types import SimpleNamespace
 
 import pytest
 
+import pre_commit_hooks.check_shebang_scripts_are_executable as shebang_hook
 from pre_commit_hooks.check_shebang_scripts_are_executable import \
     _check_git_filemode
 from pre_commit_hooks.check_shebang_scripts_are_executable import main
@@ -87,3 +90,51 @@ def test_git_executable_shebang(temp_git_dir, content, mode, expected):
         filenames = [path for path in [str(path)] if os.access(path, os.X_OK)]
 
         assert main(filenames) == expected
+
+
+@pytest.mark.parametrize(
+    ('content', 'executable', 'expected'),
+    (
+        ('#!/bin/sh\n', False, 1),
+        ('#!/bin/sh\n', True, 0),
+        ('echo hello\n', False, 0),
+    ),
+)
+def test_without_git_repository(tmp_path, monkeypatch, content, executable, expected):
+    script = tmp_path / 'example.sh'
+    script.write_text(content)
+    monkeypatch.chdir(tmp_path)
+    monkeypatch.setattr(
+        shebang_hook, 'os',
+        SimpleNamespace(access=lambda path, mode: executable, X_OK=os.X_OK),
+    )
+    monkeypatch.setattr(
+        shebang_hook, 'sys', SimpleNamespace(platform='linux', stderr=sys.stderr),
+    )
+
+    assert main([str(script)]) == expected
+
+
+def test_without_git_repository_on_windows_raises(tmp_path, monkeypatch):
+    script = tmp_path / 'example.sh'
+    script.write_text('#!/bin/sh\n')
+    monkeypatch.chdir(tmp_path)
+    monkeypatch.setattr(
+        shebang_hook, 'sys', SimpleNamespace(platform='win32', stderr=sys.stderr),
+    )
+
+    with pytest.raises(shebang_hook.CalledProcessError):
+        main([str(script)])
+
+
+def test_git_failure_inside_repository_is_not_hidden(tmp_path, monkeypatch):
+    monkeypatch.chdir(tmp_path)
+    cmd_output('git', 'init', '.')
+
+    def broken_ls_files(paths):
+        raise shebang_hook.CalledProcessError('simulated git error')
+
+    monkeypatch.setattr(shebang_hook, 'git_ls_files', broken_ls_files)
+
+    with pytest.raises(shebang_hook.CalledProcessError, match='simulated'):
+        main([])