diff --git a/rh/hooks.py b/rh/hooks.py
index d07e0f9..e31cc48 100644
--- a/rh/hooks.py
+++ b/rh/hooks.py
@@ -353,24 +353,24 @@
     exclude_list = [fr'^{x}/.*$' for dir_list in exclude_dirs for x in dir_list]
 
     # Filter diff based on extension.
-    include_list = [
+    extensions = frozenset((
         # Coding languages and scripts.
-        r".*\.c$",
-        r".*\.cc$",
-        r".*\.cpp$",
-        r".*\.h$",
-        r".*\.java$",
-        r".*\.kt$",
-        r".*\.rs$",
-        r".*\.py$",
-        r".*\.sh$",
+        'c',
+        'cc',
+        'cpp',
+        'h',
+        'java',
+        'kt',
+        'rs',
+        'py',
+        'sh',
 
         # Build and config files.
-        r".*\.bp$",
-        r".*\.mk$",
-        r".*\.xml$",
-    ]
-    diff = _filter_diff(diff, include_list, exclude_list)
+        'bp',
+        'mk',
+        'xml',
+    ))
+    diff = _filter_diff(diff, [r'\.(' + '|'.join(extensions) + r')$'], exclude_list)
 
     # Only check the new-added files.
     diff = [d for d in diff if d.status == 'A']
@@ -378,7 +378,7 @@
     if not diff:
         return None
 
-    cmd = [get_helper_path('check_aosp_license.py'), '--commit_hash', commit]
+    cmd = [get_helper_path('check_aosp_license.py'), '--commit-hash', commit]
     cmd += HookOptions.expand_vars(('${PREUPLOAD_FILES}',), diff)
     return _check_cmd('aosp_license', project, commit, cmd)
 
diff --git a/tools/check_aosp_license.py b/tools/check_aosp_license.py
index 39896e7..81fadb5 100755
--- a/tools/check_aosp_license.py
+++ b/tools/check_aosp_license.py
@@ -20,6 +20,7 @@
 import os
 import re
 import sys
+from typing import List
 
 _path = os.path.realpath(__file__ + '/../..')
 if sys.path[0] != _path:
@@ -54,7 +55,7 @@
 )
 
 
-license_re = re.compile(AOSP_LICENSE_HEADER, re.MULTILINE)
+LICENSE_RE = re.compile(AOSP_LICENSE_HEADER, re.MULTILINE)
 
 
 AOSP_LICENSE_SUBSTR = 'Licensed under the Apache License'
@@ -62,22 +63,19 @@
 
 def check_license(contents: str) -> bool:
     """Verifies the AOSP license/copyright header."""
-    return license_re.search(contents) is not None
+    return LICENSE_RE.search(contents) is not None
 
 
 def get_parser() -> argparse.ArgumentParser:
-    parser = argparse.ArgumentParser(
-        description=(
-            'Check if the given files in a given commit has an AOSP license.'
-        )
-    )
+    """Returns a command line parser."""
+    parser = argparse.ArgumentParser(description=__doc__)
     parser.add_argument(
-        'file_paths',
+        'files',
         nargs='+',
         help='The file paths to check.',
     )
     parser.add_argument(
-        '--commit_hash',
+        '--commit-hash',
         '-c',
         help='The commit hash to check.',
         # TODO(b/370907797): Read the contents on the file system by default
@@ -87,26 +85,23 @@
     return parser
 
 
-def main(argv: list[str]):
+def main(argv: List[str]) -> int:
     """The main entry."""
     parser = get_parser()
-    args = parser.parse_args(argv)
-    commit_hash = args.commit_hash
-    file_paths = args.file_paths
+    opts = parser.parse_args(argv)
+    commit_hash = opts.commit_hash
+    file_paths = opts.file_paths
 
     all_passed = True
     for file_path in file_paths:
         contents = rh.git.get_file_content(commit_hash, file_path)
         if not check_license(contents):
-            has_pattern = contents.find(AOSP_LICENSE_SUBSTR) != -1
-            if has_pattern:
-                print(f'Malformed AOSP license in {file_path}')
+            if AOSP_LICENSE_SUBSTR in contents:
+                print(f'{file_path}: Malformed AOSP license', file=sys.stderr)
             else:
-                print(f'Missing AOSP license in {file_path}')
+                print(f'{file_path}: Missing AOSP license', file=sys.stderr)
             all_passed = False
-    if not all_passed:
-        return 1
-    return 0
+    return 0 if all_passed else 1
 
 
 if __name__ == '__main__':