diff --git a/modules/cli/default.nix b/modules/cli/default.nix
index a24d1b8..d491fda 100644
--- a/modules/cli/default.nix
+++ b/modules/cli/default.nix
@@ -89,6 +89,9 @@
   programs.tmux = {
     enable = true;
     terminal = "screen-256color";
+    extraConfig = ''
+      set-environment -gu SHLVL
+    '';
   };
 
   programs.bash.interactiveShellInit = ''