diff --git a/pre_commit_hooks/enforce_branch_name.py b/pre_commit_hooks/enforce_branch_name.py
index 170e1c2..6d442d9 100644
--- a/pre_commit_hooks/enforce_branch_name.py
+++ b/pre_commit_hooks/enforce_branch_name.py
@@ -14,25 +14,25 @@ ERROR = 1
 
 def branch_follows_pattern(patterns: AbstractSet[str]) -> bool:
     try:
-        ref_name = cmd_output("git", "symbolic-ref", "HEAD")
+        ref_name = cmd_output('git', 'symbolic-ref', 'HEAD')
     except CalledProcessError:
         return False
-    chunks = ref_name.strip().split("/")
-    branch_name = "/".join(chunks[2:])
+    chunks = ref_name.strip().split('/')
+    branch_name = '/'.join(chunks[2:])
     return any(re.match(p, branch_name) for p in patterns)
 
 
 def main(argv: Sequence[str] | None = None) -> int:
     parser = argparse.ArgumentParser()
     parser.add_argument(
-        "-p",
-        "--pattern",
-        action="append",
-        help=("regex pattern that the name of the branch must comply with"),
+        '-p',
+        '--pattern',
+        action='append',
+        help=('regex pattern that the name of the branch must comply with'),
     )
     args = parser.parse_args(argv)
     return OK if branch_follows_pattern(frozenset(args.pattern)) else ERROR
 
 
-if __name__ == "__main__":
+if __name__ == '__main__':
     raise SystemExit(main())