diff --git a/scripts/setup/upgrade-postgresql b/scripts/setup/upgrade-postgresql
index f8d91bf710..d75deb6d17 100755
--- a/scripts/setup/upgrade-postgresql
+++ b/scripts/setup/upgrade-postgresql
@@ -12,7 +12,8 @@ export LC_ALL=C.UTF-8
 export LANG=C.UTF-8
 export LANGUAGE=C.UTF-8
 
-UPGRADE_TO=${1:-15}
+LATEST_SUPPORTED_VERSION=15
+UPGRADE_TO=${1:-$LATEST_SUPPORTED_VERSION}
 UPGRADE_FROM=$(crudini --get /etc/zulip/zulip.conf postgresql version)
 ZULIP_PATH="$(dirname "$0")/../.."
 
@@ -26,6 +27,12 @@ if [[ "$UPGRADE_TO" -lt "$UPGRADE_FROM" ]]; then
     exit 1
 fi
 
+if [[ "$UPGRADE_TO" -gt "$LATEST_SUPPORTED_VERSION" ]]; then
+    echo "This version of Zulip does not support PostgreSQL $UPGRADE_TO."
+    echo "You may need to upgrade Zulip before you can upgrade to PostgreSQL $UPGRADE_TO."
+    exit 1
+fi
+
 # Verify that the version in /etc/zulip/zulip.conf is the version that
 # Django actually stores its data in.  We can only do that if the
 # database server is on the same host as the application server.