diff --git a/nixos/programs/zsh.nix b/nixos/programs/zsh.nix
index 11a2952f..3c5d26e0 100644
--- a/nixos/programs/zsh.nix
+++ b/nixos/programs/zsh.nix
@@ -45,7 +45,7 @@
         export PATH="$HOME/.yarn/bin:$HOME/.config/yarn/global/node_modules/.bin:$PATH";
       '';
       envExtra = ''
-        if [[ -z `nixos-version` ]]; then
+        if [[ ! -x nixos-version ]]; then
           source /home/cyryl/.nix-profile/etc/profile.d/nix.sh
           export NIX_PATH="$HOME/.nix-defexpr/channels:$NIX_PATH"
           echo "non-nixos patches loaded"