mercurial/revset.py

--- a/mercurial/revset.py	Mon May 07 14:32:43 2018 -0700
+++ b/mercurial/revset.py	Mon May 07 14:32:55 2018 -0700
@@ -1333,7 +1333,7 @@
     else:
         rn = None
         try:
-            pm = repo.changelog._partialmatch(n)
+            pm = scmutil.resolvehexnodeidprefix(repo, n)
             if pm is not None:
                 rn = repo.changelog.rev(pm)
         except LookupError: