diff --git a/phpBB/includes/template/compile.php b/phpBB/includes/template/compile.php
index 4132fb2e34..18a52e87a6 100644
--- a/phpBB/includes/template/compile.php
+++ b/phpBB/includes/template/compile.php
@@ -54,6 +54,7 @@ class phpbb_template_filter extends php_user_filter
 	public function filter($in, $out, &$consumed, $closing)
 	{
 		$written = false;
+		$first = false;
 
 		while ($bucket = stream_bucket_make_writeable($in))
 		{
@@ -71,7 +72,13 @@ class phpbb_template_filter extends php_user_filter
 
 			$written = true;
 
-			$bucket->data = $this->compile($data);
+			$data = $this->compile($data);
+			if (!$first)
+			{
+				$data = $this->prepend_preamble($data);
+				$first = false;
+			}
+			$bucket->data = $data;
 			$bucket->datalen = strlen($bucket->data);
 			stream_bucket_append($out, $bucket);
 		}
@@ -150,6 +157,18 @@ class phpbb_template_filter extends php_user_filter
 		return $data;
 	}
 
+	/**
+	* Prepends a preamble to compiled template.
+	* Currently preamble checks if IN_PHPBB is defined and calls exit() if it is not.
+	* @param string $data Compiled template chunk
+	* @return string Compiled template chunk with preamble prepended
+	*/
+	private function prepend_preamble($data)
+	{
+		$data = "<?php if (!defined('IN_PHPBB')) exit;" . ((strncmp($data, '<?php', 5) === 0) ? substr($data, 5) : ' ?>' . $data);
+		return $data;
+	}
+
 	private function replace($matches)
 	{
 		if ($this->in_php && $matches[1] != 'ENDPHP')
diff --git a/tests/template/template_compile_test.php b/tests/template/template_compile_test.php
new file mode 100644
index 0000000000..2f12292870
--- /dev/null
+++ b/tests/template/template_compile_test.php
@@ -0,0 +1,32 @@
+<?php
+/**
+*
+* @package testing
+* @copyright (c) 2008 phpBB Group
+* @license http://opensource.org/licenses/gpl-license.php GNU Public License
+*
+*/
+
+require_once dirname(__FILE__) . '/../../phpBB/includes/functions.php';
+require_once dirname(__FILE__) . '/../../phpBB/includes/template.php';
+
+class phpbb_template_template_compile_test extends phpbb_test_case
+{
+	private $template_compile;
+	private $template_path;
+
+	protected function setUp()
+	{
+		$this->template_compile = new phpbb_template_compile();
+		$this->template_path = dirname(__FILE__) . '/templates';
+	}
+
+	public function test_in_phpbb()
+	{
+		$output = $this->template_compile->compile_file($this->template_path . '/trivial.html');
+		$this->assertTrue(strlen($output) > 0);
+		$statements = explode(';', $output);
+		$first_statement = $statements[0];
+		$this->assertTrue(!!preg_match('#if.*defined.*IN_PHPBB.*exit#', $first_statement));
+	}
+}
diff --git a/tests/template/templates/trivial.html b/tests/template/templates/trivial.html
new file mode 100644
index 0000000000..3a1c1c5324
--- /dev/null
+++ b/tests/template/templates/trivial.html
@@ -0,0 +1 @@
+This is a trivial template.