mercurial/commands.py

--- a/mercurial/commands.py	Tue Jan 16 21:42:42 2018 +0900
+++ b/mercurial/commands.py	Tue Jan 16 21:51:27 2018 +0900
@@ -5530,7 +5530,8 @@
 
         # if we defined a bookmark, we have to remember the original name
         brev = rev
-        repo = scmutil.unhidehashlikerevs(repo, [rev], 'nowarn')
+        if rev:
+            repo = scmutil.unhidehashlikerevs(repo, [rev], 'nowarn')
         ctx = scmutil.revsingle(repo, rev, rev)
         rev = ctx.rev()
         if ctx.hidden():