diff --git a/scripts/nix-profile-daemon.sh.in b/scripts/nix-profile-daemon.sh.in
index c63db4648..d256b24ed 100644
--- a/scripts/nix-profile-daemon.sh.in
+++ b/scripts/nix-profile-daemon.sh.in
@@ -31,7 +31,7 @@ fi
 export NIX_PROFILES="@localstatedir@/nix/profiles/default $NIX_LINK"
 
 # Populate bash completions, .desktop files, etc
-if [ -z "$XDG_DATA_DIRS" ]; then
+if [ -z "${XDG_DATA_DIRS-}" ]; then
     # According to XDG spec the default is /usr/local/share:/usr/share, don't set something that prevents that default
     export XDG_DATA_DIRS="/usr/local/share:/usr/share:$NIX_LINK/share:/nix/var/nix/profiles/default/share"
 else
diff --git a/scripts/nix-profile.sh.in b/scripts/nix-profile.sh.in
index 56e070ae1..44bc96e89 100644
--- a/scripts/nix-profile.sh.in
+++ b/scripts/nix-profile.sh.in
@@ -33,7 +33,7 @@ if [ -n "$HOME" ] && [ -n "$USER" ]; then
     export NIX_PROFILES="@localstatedir@/nix/profiles/default $NIX_LINK"
 
     # Populate bash completions, .desktop files, etc
-    if [ -z "$XDG_DATA_DIRS" ]; then
+    if [ -z "${XDG_DATA_DIRS-}" ]; then
         # According to XDG spec the default is /usr/local/share:/usr/share, don't set something that prevents that default
         export XDG_DATA_DIRS="/usr/local/share:/usr/share:$NIX_LINK/share:/nix/var/nix/profiles/default/share"
     else