diff --git a/libcanberra/repos/extra-i686/libcanberra.xinit b/libcanberra/repos/extra-i686/libcanberra.xinit
index 2511e9f..98d2daf 100644
--- a/libcanberra/repos/extra-i686/libcanberra.xinit
+++ b/libcanberra/repos/extra-i686/libcanberra.xinit
@@ -1,12 +1,12 @@
 #!/bin/bash
 
-case "$DESKTOP_SESSION" in
+case "${DESKTOP_SESSION-}" in
   gnome) # Done by gnome-settings-daemon
   ;;
   *)
     # Extra check in case DESKTOP_SESSION is not set correctly
-    if [[ -z $GNOME_DESKTOP_SESSION_ID ]]; then
-      if [[ -z $GTK_MODULES ]]; then
+    if [[ -z ${GNOME_DESKTOP_SESSION_ID-} ]]; then
+      if [[ -z ${GTK_MODULES-} ]]; then
         GTK_MODULES="canberra-gtk-module"
       else
         GTK_MODULES="$GTK_MODULES:canberra-gtk-module"
diff --git a/libcanberra/repos/extra-x86_64/libcanberra.xinit b/libcanberra/repos/extra-x86_64/libcanberra.xinit
index 2511e9f..98d2daf 100644
--- a/libcanberra/repos/extra-x86_64/libcanberra.xinit
+++ b/libcanberra/repos/extra-x86_64/libcanberra.xinit
@@ -1,12 +1,12 @@
 #!/bin/bash
 
-case "$DESKTOP_SESSION" in
+case "${DESKTOP_SESSION-}" in
   gnome) # Done by gnome-settings-daemon
   ;;
   *)
     # Extra check in case DESKTOP_SESSION is not set correctly
-    if [[ -z $GNOME_DESKTOP_SESSION_ID ]]; then
-      if [[ -z $GTK_MODULES ]]; then
+    if [[ -z ${GNOME_DESKTOP_SESSION_ID-} ]]; then
+      if [[ -z ${GTK_MODULES-} ]]; then
         GTK_MODULES="canberra-gtk-module"
       else
         GTK_MODULES="$GTK_MODULES:canberra-gtk-module"
diff --git a/libcanberra/trunk/libcanberra.xinit b/libcanberra/trunk/libcanberra.xinit
index 2511e9f..98d2daf 100644
--- a/libcanberra/trunk/libcanberra.xinit
+++ b/libcanberra/trunk/libcanberra.xinit
@@ -1,12 +1,12 @@
 #!/bin/bash
 
-case "$DESKTOP_SESSION" in
+case "${DESKTOP_SESSION-}" in
   gnome) # Done by gnome-settings-daemon
   ;;
   *)
     # Extra check in case DESKTOP_SESSION is not set correctly
-    if [[ -z $GNOME_DESKTOP_SESSION_ID ]]; then
-      if [[ -z $GTK_MODULES ]]; then
+    if [[ -z ${GNOME_DESKTOP_SESSION_ID-} ]]; then
+      if [[ -z ${GTK_MODULES-} ]]; then
         GTK_MODULES="canberra-gtk-module"
       else
         GTK_MODULES="$GTK_MODULES:canberra-gtk-module"