diff -r c420792217c8 -r 430fdb717549 mercurial/policy.py
--- a/mercurial/policy.py	Sat Mar 03 12:39:11 2018 -0800
+++ b/mercurial/policy.py	Sat Mar 03 12:39:14 2018 -0800
@@ -66,7 +66,7 @@
 # keep in sync with "version" in C modules
 _cextversions = {
     (r'cext', r'base85'): 1,
-    (r'cext', r'bdiff'): 2,
+    (r'cext', r'bdiff'): 3,
     (r'cext', r'diffhelpers'): 1,
     (r'cext', r'mpatch'): 1,
     (r'cext', r'osutil'): 3,