diff --git a/installer/mac/preinstall.sh b/installer/mac/preinstall.sh
index acac19a4..4fdaa4d7 100755
--- a/installer/mac/preinstall.sh
+++ b/installer/mac/preinstall.sh
@@ -12,7 +12,7 @@ delete_app()
 compare_versions()
 {
     # Get the installer version:
-    CURRENT_VERSION=${APP_VERSION}
+    CURRENT_VERSION=APP_VERSION
 
     # Get the currently installed version:
     INSTALLED_VERSION=$(plutil -p /Applications/Symphony.app/Contents/Info.plist | awk '/CFBundleShortVersionString/ {print substr($3, 2, length($3)-2)}')