diff --git a/src/filelock/_unix.py b/src/filelock/_unix.py
index c2e270e8..4c0a2603 100644
--- a/src/filelock/_unix.py
+++ b/src/filelock/_unix.py
@@ -35,7 +35,7 @@ def _acquire(self) -> None:
             open_flags = os.O_RDWR | os.O_CREAT | os.O_TRUNC
             fd = os.open(self._lock_file, open_flags, self._mode)
             try:
-                os.chmod(fd, self._mode)
+                os.fchmod(fd, self._mode)
             except PermissionError:
                 pass  # This locked is not owned by this UID
             try:
diff --git a/whitelist.txt b/whitelist.txt
index d5c4d2e4..90d6069e 100644
--- a/whitelist.txt
+++ b/whitelist.txt
@@ -5,6 +5,7 @@ caplog
 eacces
 enosys
 extlinks
+fchmod
 filelock
 filemode
 fspath