diff --git a/win/copy_cdb_to_output.py b/win/copy_cdb_to_output.py
index c3c2581e4..d41dd40ae 100755
--- a/win/copy_cdb_to_output.py
+++ b/win/copy_cdb_to_output.py
@@ -23,6 +23,7 @@ def _HexDigest(file_name):
   while len(buf) > 0:
     hasher.update(buf)
     buf = afile.read(blocksize)
+  afile.close()
   return hasher.hexdigest()