diff --git a/bin/setup-hg-evolve b/bin/setup-hg-evolve
--- a/bin/setup-hg-evolve
+++ b/bin/setup-hg-evolve
@@ -12,3 +12,6 @@ if ! grep -qsw evolve ~/.hgext/hgrc; the
   printf '[extensions]\nevolve =\n' >> ~/.hgext/hgrc
 fi
 
+if ! grep -qsw topic ~/.hgext/hgrc; then
+  printf '[extensions]\ntopic =\n' >> ~/.hgext/hgrc
+fi