diff --git a/changelog/.gitkeep b/changelog/.gitkeep
new file mode 100644
index 00000000..e69de29b
diff --git a/make-release.sh b/make-release.sh
index ca2069be..a096dc3b 100755
--- a/make-release.sh
+++ b/make-release.sh
@@ -8,8 +8,9 @@ else
 fi
 
 git checkout -b "release/$1"
-sed -i "s/## \\[Unreleased\\]/## \\[Unreleased\\]\\n\\n## \\[$1\\] - $(date +%Y-%m-%d)/" CHANGELOG.md
-sed -i "s/const SMARTY_VERSION = '[^']\+';/const SMARTY_VERSION = '$1';/" src/Smarty.php
+
+php utilities/update-changelog.php $1
+php utilities/update-smarty-version-number.php $1
 
 git add CHANGELOG.md src/Smarty.php
 git commit -m "version bump"
diff --git a/utilities/update-changelog.php b/utilities/update-changelog.php
new file mode 100644
index 00000000..f5b9534f
--- /dev/null
+++ b/utilities/update-changelog.php
@@ -0,0 +1,42 @@
+<?php
+
+// This takes the *.md files in changelog/ dir and inserts them
+// right below the '## [Unreleased]' marker in CHANGELOG.md
+
+$path_to_main_changelog = 'CHANGELOG.md';
+$marker = '## [Unreleased]';
+$changelog_files_pattern = 'changelog/*.md';
+$new_version = $argv[1];
+
+$file_contents = file_get_contents($path_to_main_changelog);
+
+foreach (glob($changelog_files_pattern) as $filename) {
+    $content_to_insert = file_get_contents($filename);
+
+    if (!endsWithNewline($content_to_insert)) {
+        $content_to_insert .= "\n";
+    }
+
+    $file_contents = str_replace(
+        $marker,
+        $marker . $content_to_insert,
+        $file_contents
+    );
+    unlink($filename);
+}
+
+
+// add the version number and date
+$file_contents = str_replace(
+    $marker,
+    $marker . sprintf("\n\n## [%s] - %s\n", $new_version, date('Y-m-d')),
+    $file_contents
+);
+
+file_put_contents($path_to_main_changelog, $file_contents);
+
+
+function endsWithNewline($str): bool
+{
+    return preg_match('/[\r\n]$/', $str) === 1;
+}
\ No newline at end of file
diff --git a/utilities/update-smarty-version-number.php b/utilities/update-smarty-version-number.php
new file mode 100644
index 00000000..b3d2529c
--- /dev/null
+++ b/utilities/update-smarty-version-number.php
@@ -0,0 +1,11 @@
+<?php
+
+// This takes the Smarty class file and updates the SMARTY_VERSION constant
+
+$path_to_smarty_class = 'src/Smarty.php';
+$pattern = "/const SMARTY_VERSION = '[^']+'/";
+$replacement = "const SMARTY_VERSION = '" . $argv[1] . "'";
+
+$file_contents = preg_replace($pattern, $replacement, file_get_contents($path_to_smarty_class));
+
+file_put_contents($path_to_smarty_class, $file_contents);