diff --git a/scripts/nix-profile-daemon.fish.in b/scripts/nix-profile-daemon.fish.in
index 3fe9e782a6b..c23aa64f0a8 100644
--- a/scripts/nix-profile-daemon.fish.in
+++ b/scripts/nix-profile-daemon.fish.in
@@ -20,7 +20,7 @@ set __ETC_PROFILE_NIX_SOURCED 1
 set --export NIX_PROFILES "@localstatedir@/nix/profiles/default $HOME/.nix-profile"
 
 # Populate bash completions, .desktop files, etc
-if test -n "$XDG_DATA_DIRS"
+if test -z "$XDG_DATA_DIRS"
     # According to XDG spec the default is /usr/local/share:/usr/share, don't set something that prevents that default
     set --export XDG_DATA_DIRS "/usr/local/share:/usr/share:/nix/var/nix/profiles/default/share"
 else
diff --git a/scripts/nix-profile-daemon.sh.in b/scripts/nix-profile-daemon.sh.in
index 3089cec663d..c63db464866 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 [ -n "${XDG_DATA_DIRS-}" ]; then
+if [ -z "$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:$NIX_LINK/share:/nix/var/nix/profiles/default/share"
 else
diff --git a/scripts/nix-profile.fish.in b/scripts/nix-profile.fish.in
index 2523594f26f..619df52b895 100644
--- a/scripts/nix-profile.fish.in
+++ b/scripts/nix-profile.fish.in
@@ -21,7 +21,7 @@ if test -n "$HOME" && test -n "$USER"
     set --export NIX_PROFILES "@localstatedir@/nix/profiles/default $HOME/.nix-profile"
 
     # Populate bash completions, .desktop files, etc
-    if test -n "$XDG_DATA_DIRS"
+    if test -z "$XDG_DATA_DIRS"
         # According to XDG spec the default is /usr/local/share:/usr/share, don't set something that prevents that default
         set --export XDG_DATA_DIRS "/usr/local/share:/usr/share:$NIX_LINK/share:/nix/var/nix/profiles/default/share"
     else
diff --git a/scripts/nix-profile.sh.in b/scripts/nix-profile.sh.in
index a0d09858841..56e070ae19b 100644
--- a/scripts/nix-profile.sh.in
+++ b/scripts/nix-profile.sh.in
@@ -33,7 +33,7 @@ if [ -n "$HOME" ] && [ -n "$USER" ]; then
     export NIX_PROFILES="@localstatedir@/nix/profiles/default $NIX_LINK"
 
     # Populate bash completions, .desktop files, etc
-    if [ -n "${XDG_DATA_DIRS-}" ]; then
+    if [ -z "$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