diff --git a/contrib/perf.py b/contrib/perf.py
--- a/contrib/perf.py
+++ b/contrib/perf.py
@@ -575,8 +575,8 @@ def perffncachewrite(ui, repo, **opts):
         s.fncache._dirty = True
         s.fncache.write(tr)
     timer(d)
+    tr.close()
     lock.release()
-    tr.close()
     fm.end()
 
 @command('perffncacheencode', formatteropts)