diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -1166,7 +1166,7 @@
             wctx.copy(origsrc, dst)
 
 def writerequires(opener, requirements):
-    with opener('requires', 'w') as fp:
+    with opener('requires', 'w', atomictemp=True) as fp:
         for r in sorted(requirements):
             fp.write("%s\n" % r)