diff --git a/kallithea/lib/vcs/backends/hg/changeset.py b/kallithea/lib/vcs/backends/hg/changeset.py
--- a/kallithea/lib/vcs/backends/hg/changeset.py
+++ b/kallithea/lib/vcs/backends/hg/changeset.py
@@ -88,7 +88,11 @@ class MercurialChangeset(BaseChangeset):
 
     @LazyProperty
     def successors(self):
-        successors = obsolete.successorssets(self._ctx._repo, self._ctx.node())
+        try:
+            from mercurial import obsutil
+            successors = obsutil.successorssets(self._ctx._repo, self._ctx.node())
+        except ImportError:  # moved in Mercurial 4.3 (4f49810a1011)
+            successors = obsolete.successorssets(self._ctx._repo, self._ctx.node())
         if successors:
             # flatten the list here handles both divergent (len > 1)
             # and the usual case (len = 1)
diff --git a/kallithea/tests/vcs/test_hg.py b/kallithea/tests/vcs/test_hg.py
--- a/kallithea/tests/vcs/test_hg.py
+++ b/kallithea/tests/vcs/test_hg.py
@@ -585,7 +585,6 @@ class TestMercurialChangeset(object):
         assert 'Lukasz Balcerzak' == self.repo.get_changeset('3803844fdbd3').author_name
         assert 'marcink' == self.repo.get_changeset('84478366594b').author_name
 
-    @pytest.mark.xfail
     def test_successors(self):
         init_chset = self.repo.get_changeset(0)
         assert init_chset.successors == []