diff --git a/nixos/programs/zsh.nix b/nixos/programs/zsh.nix
index 06663005..c2bd0a41 100644
--- a/nixos/programs/zsh.nix
+++ b/nixos/programs/zsh.nix
@@ -46,7 +46,7 @@
       '';
       envExtra = ''
         local nixos_version=`which nixos-version`
-        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"