diff --git a/nix/dev-shell.nix b/nix/dev-shell.nix
--- a/nix/dev-shell.nix
+++ b/nix/dev-shell.nix
@@ -137,8 +137,6 @@
     ${../scripts}/install_homebrew_macos.sh
 
     ${../scripts}/install_homebrew_deps.sh watchman
-
-    ${../scripts}/prompt_direnv_macos.sh
   '' + ''
 
     # Render default configuration for keyserver
diff --git a/scripts/install_nix.sh b/scripts/install_nix.sh
--- a/scripts/install_nix.sh
+++ b/scripts/install_nix.sh
@@ -121,6 +121,11 @@
 
 # Ask user if they would like to use Powerline for bash prompt
 SCRIPT_DIR=$(cd "$(dirname "$0")" || true; pwd -P)
+
+if [[ "$OSTYPE" == 'darwin'* ]]; then
+  "$SCRIPT_DIR"/prompt_direnv_macos.sh
+fi
+
 # Build the nixified script which is aware of Powerline and dependencies
 nix build "$SCRIPT_DIR"'/..#better-prompt'
 # Source file to apply Powerline bootstrap logic
diff --git a/scripts/prompt_direnv_macos.sh b/scripts/prompt_direnv_macos.sh
--- a/scripts/prompt_direnv_macos.sh
+++ b/scripts/prompt_direnv_macos.sh
@@ -21,7 +21,7 @@
 # `test -t` tests if a file descriptor is open, 0 being stdin
 # Normally, a non-interactive shell will not have 0 FD bound
 # However, Buildkite still has 0 FD bound, so check if PS1 is empty
-if [[ ! -t 0 ]] || [[ -z "${PS1-}" ]]; then
+if [[ ! -t 0 ]]; then
   exit 0
 fi