diff --git a/ops/nixos/lib/hgrc.nix b/ops/nixos/lib/hgrc.nix
index 7b860a7bcb..2a93c38e99 100644
--- a/ops/nixos/lib/hgrc.nix
+++ b/ops/nixos/lib/hgrc.nix
@@ -50,6 +50,7 @@ let
     remotenames =
     amend =
     evolve =
+    topic =
   '';
 in
 {