--- a/hgext3rd/topic/__init__.py	Tue Jul 25 04:19:55 2017 +0200
+++ b/hgext3rd/topic/__init__.py	Tue Jul 25 05:14:37 2017 +0200
@@ -656,11 +656,14 @@
 def checkt0(orig, ui, repo, node=None, rev=None, *args, **kwargs):
 
     thezeros = set(['t0', 'b0'])
-    overrides = {}
-    if node in thezeros or rev in thezeros:
-        overrides[('_internal', 'keep-topic')] = 'yes'
-    with repo.ui.configoverride(overrides, source='topic-extension'):
+    backup = repo.ui.backupconfig('_internal', 'keep-topic')
+    try:
+        if node in thezeros or rev in thezeros:
+            repo.ui.setconfig('_internal', 'keep-topic', 'yes',
+                              source='topic-extension')
         return orig(ui, repo, node, rev, *args, **kwargs)
+    finally:
+        repo.ui.restoreconfig(backup)
 
 def _fixrebase(loaded):
     if not loaded: