diff --git a/scripts/nix-profile.sh.in b/scripts/nix-profile.sh.in
index e868399b1..1b73e1de4 100644
--- a/scripts/nix-profile.sh.in
+++ b/scripts/nix-profile.sh.in
@@ -1,5 +1,5 @@
 # This file is tested by tests/installer/default.nix.
-if [ -n "$HOME" ] && [ -n "$USER" ]; then
+if [ -n "${HOME-}" ] && [ -n "${USER-}" ]; then
 
     # Set up the per-user profile.