Fix #4015
diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index 57693e1..459c8f5 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -804,11 +804,12 @@
 	 *
 	 * @param	string
 	 * @param	string
-	 * @return	void
+	 * @return	CI_Email
 	 */
 	public function set_header($header, $value)
 	{
 		$this->_headers[$header] = str_replace(array("\n", "\r"), '', $value);
+		return $this;
 	}
 
 	// --------------------------------------------------------------------