diff --git a/scripts/nix-profile-daemon.sh.in b/scripts/nix-profile-daemon.sh.in
index eb124c0b5..59c00d491 100644
--- a/scripts/nix-profile-daemon.sh.in
+++ b/scripts/nix-profile-daemon.sh.in
@@ -52,7 +52,7 @@ elif [ -e /etc/pki/tls/certs/ca-bundle.crt ]; then # Fedora, CentOS
 else
   # Fall back to what is in the nix profiles, favouring whatever is defined last.
   check_nix_profiles() {
-    if [ -n "$ZSH_VERSION" ]; then
+    if [ -n "${ZSH_VERSION:-}" ]; then
       # Zsh by default doesn't split words in unquoted parameter expansion.
       # Set local_options for these options to be reverted at the end of the function
       # and shwordsplit to force splitting words in $NIX_PROFILES below.
diff --git a/tests/installer/default.nix b/tests/installer/default.nix
index 4aed6eae4..7c82045ad 100644
--- a/tests/installer/default.nix
+++ b/tests/installer/default.nix
@@ -217,10 +217,16 @@ let
         $ssh <<EOF
           set -ex
 
+          # enable nounset while loading the profile
+          # this may or may not work on all distros, depending on the quality of their scripts
+          set -u
+
           # FIXME: get rid of this; ideally ssh should just work.
           source ~/.bash_profile || true
           source ~/.bash_login || true
           source ~/.profile || true
+          set +u
+
           source /etc/bashrc || true
 
           nix-env --version