--- a/pylib/mozhg/mozhg/rewrite.py
+++ b/pylib/mozhg/mozhg/rewrite.py
@@ -13,18 +13,21 @@ import mercurial.hg as hg
 import mercurial.lock as lockmod
 import mercurial.obsolete as obsolete
 import mercurial.phases as phases
 import mercurial.repair as repair
 import mercurial.util as util
 
 
 # Mercurial 3.5 renamed readcurrent to readactive.
+# Mercurial 3.7 renamed readactive to _readactive.
 def activebookmark(repo):
-    if hasattr(bookmarks, 'readactive'):
+    if hasattr(repo, '_activebookmark'):
+        return repo._activebookmark
+    elif hasattr(bookmarks, 'readactive'):
         return bookmarks.readactive(repo)
     else:
         return bookmarks.readcurrent(repo)
 
 
 def newparents(repo, ctx, revmap):
     """Obtain the parent nodes of a potentially rewritten changeset.