--- a/mercurial/revlog.py	Tue Apr 24 13:55:25 2018 -0700
+++ b/mercurial/revlog.py	Wed Apr 25 09:24:07 2018 -0700
@@ -1466,7 +1466,7 @@
         if id in self._pcache:
             return self._pcache[id]
 
-        if len(id) < 40:
+        if len(id) <= 40:
             try:
                 # hex(node)[:...]
                 l = len(id) // 2  # grab an even number of digits