diff --git a/setup/preflight.sh b/setup/preflight.sh
index a4e7b5cf..600b4188 100644
--- a/setup/preflight.sh
+++ b/setup/preflight.sh
@@ -8,13 +8,14 @@ if [[ $EUID -ne 0 ]]; then
 	exit 1
 fi
 
-. /etc/os-release
-
 # Check that we are running on Ubuntu 22.04 LTS (or 22.04.xx).
-if [ "${ID:-}" != "ubuntu" ] || [ "${VERSION_ID:-}" != "22.04" ]; then
+# Pull in the variables defined in /etc/os-release but in a
+# namespace to avoid polluting our variables.
+source <(cat /etc/os-release | sed s/^/OS_RELEASE_/)
+if [ "${OS_RELEASE_ID:-}" != "ubuntu" ] || [ "${OS_RELEASE_VERSION_ID:-}" != "22.04" ]; then
 	echo "Mail-in-a-Box only supports being installed on Ubuntu 22.04, sorry. You are running:"
 	echo
-	echo "${ID:-"Unknown linux distribution"} ${VERSION_ID:-}"
+	echo "${OS_RELEASE_ID:-"Unknown linux distribution"} ${OS_RELEASE_VERSION_ID:-}"
 	echo
 	echo "We can't write scripts that run on every possible setup, sorry."
 	exit 1