diff -r b95b48a55c36 -r 1464183343b3 mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Fri Aug 17 16:11:35 2018 -0700
+++ b/mercurial/debugcommands.py	Wed Aug 15 15:20:44 2018 +0200
@@ -2170,7 +2170,10 @@
                     numother += 1
 
         # Obtain data on the raw chunks in the revlog.
-        segment = r._getsegmentforrevs(rev, rev)[1]
+        if util.safehasattr(r, '_getsegmentforrevs'):
+            segment = r._getsegmentforrevs(rev, rev)[1]
+        else:
+            segment = r._revlog._getsegmentforrevs(rev, rev)[1]
         if segment:
             chunktype = bytes(segment[0:1])
         else: