diff --git a/artiq/frontend/artiq_master.py b/artiq/frontend/artiq_master.py
index b63c52a2e..2d6fffd18 100755
--- a/artiq/frontend/artiq_master.py
+++ b/artiq/frontend/artiq_master.py
@@ -74,6 +74,7 @@ def main():
     else:
         repo_backend = FilesystemBackend(args.repository)
     repository = Repository(repo_backend, log.log)
+    atexit.register(repository.close)
     repository.scan_async()
 
     worker_handlers = {
diff --git a/artiq/master/repository.py b/artiq/master/repository.py
index 71eff04e1..73ff9cde0 100644
--- a/artiq/master/repository.py
+++ b/artiq/master/repository.py
@@ -63,6 +63,10 @@ class Repository:
 
         self._scanning = False
 
+    def close(self):
+        # The object cannot be used anymore after calling this method.
+        self.backend.release_rev(self.head_rev)
+
     @asyncio.coroutine
     def scan(self):
         if self._scanning: