diff --git a/lass/2configs/zsh.nix b/lass/2configs/zsh.nix
index 0a32ce510..aa3e6731d 100644
--- a/lass/2configs/zsh.nix
+++ b/lass/2configs/zsh.nix
@@ -108,7 +108,7 @@
       fi
 
       #check if in nix shell
-      if test -n "$buildInputs"; then
+      if test -n "$IN_NIX_SHELL"; then
         p_nixshell='%F{green}[s]%f '
         t_nixshell='[s] '
       else