diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -1280,7 +1280,8 @@
     """
     opts = pycompat.byteskwargs(opts)
     rev = opts.get('rev')
-    repo = scmutil.unhidehashlikerevs(repo, [rev], 'nowarn')
+    if rev:
+        repo = scmutil.unhidehashlikerevs(repo, [rev], 'nowarn')
     ctx = scmutil.revsingle(repo, rev)
     m = scmutil.match(ctx, (file1,) + pats, opts)
     fntemplate = opts.pop('output', '')