diff --git a/pikit_api/releases.py b/pikit_api/releases.py
index 0490258..5bd9c6c 100644
--- a/pikit_api/releases.py
+++ b/pikit_api/releases.py
@@ -400,6 +400,19 @@ def fetch_text_with_auth(url: str):
 def acquire_lock():
     try:
         ensure_dir(UPDATE_LOCK.parent)
+        # Clear stale lock if the recorded PID is not running
+        if UPDATE_LOCK.exists():
+            try:
+                pid = int(UPDATE_LOCK.read_text().strip() or "0")
+                if pid > 0:
+                    os.kill(pid, 0)
+                else:
+                    UPDATE_LOCK.unlink(missing_ok=True)
+            except OSError:
+                # Process not running
+                UPDATE_LOCK.unlink(missing_ok=True)
+            except Exception:
+                UPDATE_LOCK.unlink(missing_ok=True)
         lockfile = UPDATE_LOCK.open("w")
         fcntl.flock(lockfile.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
         lockfile.write(str(os.getpid()))