--- a/hgext3rd/topic/__init__.py	Thu Apr 18 11:13:39 2019 +0200
+++ b/hgext3rd/topic/__init__.py	Thu Apr 18 11:13:49 2019 +0200
@@ -1186,6 +1186,8 @@
     ist0 = False
     try:
         ret = orig(repo, node, branchmerge, force, *args, **kwargs)
+        if not hastopicext(repo):
+            return ret
         # The mergeupdatewrap function makes the destination's topic as the
         # current topic. This is right for merge but wrong for rebase. We check
         # if rebase is running and update the currenttopic to topic of new