--- a/mercurial/cmdutil.py	Sun Feb 04 14:31:32 2018 -0500
+++ b/mercurial/cmdutil.py	Sun Feb 04 15:26:49 2018 -0500
@@ -2188,12 +2188,16 @@
         mfnode = ctx.manifestnode()
         try:
             if mfnode and mfl[mfnode].find(file)[0]:
+                _prefetchfiles(repo, ctx, [file])
                 write(file)
                 return 0
         except KeyError:
             pass
 
-    for abs in ctx.walk(matcher):
+    files = [f for f in ctx.walk(matcher)]
+    _prefetchfiles(repo, ctx, files)
+
+    for abs in files:
         write(abs)
         err = 0