diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -1502,18 +1502,6 @@
 
     def shortest(self, node, minlength=1):
         """Find the shortest unambiguous prefix that matches node."""
-        def isrev(prefix):
-            try:
-                i = int(prefix)
-                # if we are a pure int, then starting with zero will not be
-                # confused as a rev; or, obviously, if the int is larger
-                # than the value of the tip rev
-                if prefix[0] == '0' or i > len(self):
-                    return False
-                return True
-            except ValueError:
-                return False
-
         def isvalid(prefix):
             try:
                 node = self._partialmatch(prefix)
@@ -1532,9 +1520,10 @@
         hexnode = hex(node)
 
         def disambiguate(hexnode, minlength):
+            """Disambiguate against wdirid."""
             for length in range(minlength, 41):
                 prefix = hexnode[:length]
-                if not isrev(prefix) and not maybewdir(prefix):
+                if not maybewdir(prefix):
                     return prefix
 
         if not getattr(self, 'filteredrevs', None):
diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -450,8 +450,30 @@
     # _partialmatch() of filtered changelog could take O(len(repo)) time,
     # which would be unacceptably slow. so we look for hash collision in
     # unfiltered space, which means some hashes may be slightly longer.
+    cl = repo.unfiltered().changelog
+
+    def isrev(prefix):
+        try:
+            i = int(prefix)
+            # if we are a pure int, then starting with zero will not be
+            # confused as a rev; or, obviously, if the int is larger
+            # than the value of the tip rev
+            if prefix[0] == '0' or i > len(cl):
+                return False
+            return True
+        except ValueError:
+            return False
+
+    def disambiguate(prefix):
+        """Disambiguate against revnums."""
+        hexnode = hex(node)
+        for length in range(len(prefix), 41):
+            prefix = hexnode[:length]
+            if not isrev(prefix):
+                return prefix
+
     try:
-        return repo.unfiltered().changelog.shortest(node, minlength)
+        return disambiguate(cl.shortest(node, minlength))
     except error.LookupError:
         raise error.RepoLookupError()