diff --git a/clang-tools-extra/clang-tidy/tool/run-clang-tidy.py b/clang-tools-extra/clang-tidy/tool/run-clang-tidy.py
index 2e796d55be8b..aa1dfc89e548 100755
--- a/clang-tools-extra/clang-tidy/tool/run-clang-tidy.py
+++ b/clang-tools-extra/clang-tidy/tool/run-clang-tidy.py
@@ -182,7 +182,7 @@ def main():
     tmpdir = tempfile.mkdtemp()
 
   # Build up a big regexy filter from all command line arguments.
-  file_name_re = re.compile('(' + ')|('.join(args.files) + ')')
+  file_name_re = re.compile('|'.join(args.files))
 
   try:
     # Spin up a bunch of tidy-launching threads.