diff --git a/make-release.sh b/make-release.sh
index b3a9df64..c8702171 100755
--- a/make-release.sh
+++ b/make-release.sh
@@ -1,6 +1,11 @@
 #!/bin/bash
 
-printf 'Creating release %s\n' "$1"
+if [[ "$1" =~ ^3\.[0-9]$ ]]; then
+   printf 'Creating release %s\n' "$1"
+else
+   echo "Invalid version number: $1. This script can only make v3.x.x releases."
+   exit 1;
+fi
 
 git checkout -b "release/$1"
 sed -i "s/## \\[Unreleased\\]/## \\[Unreleased\\]\\n\\n## \\[$1\\] - $(date +%Y-%m-%d)/" CHANGELOG.md
@@ -9,11 +14,13 @@ sed -i "s/const SMARTY_VERSION = '[^']\+';/const SMARTY_VERSION = '$1';/" libs/S
 git add CHANGELOG.md libs/Smarty.class.php
 git commit -m "version bump"
 
-git checkout master
+git checkout support/3.1
 git pull
 git merge --no-ff "release/$1"
 git branch -d "release/$1"
 git tag -a "v$1" -m "Release $1"
 
 printf 'Done creating release %s\n' "$1"
+
+# shellcheck disable=SC2016
 printf 'Run `git push --follow-tags origin` to publish it.\n'