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;
 	}
 
 	// --------------------------------------------------------------------
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index e409cc6..4e8f2f7 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -75,6 +75,7 @@
 -  Fixed a bug (#4004) - :doc:`URI Class <libraries/uri>` didn't properly parse the request URI if it contains a colon followed by a digit.
 -  Fixed a bug in :doc:`Query Builder <database/query_builder>` where the ``$escape`` parameter for some methods only affected field names.
 -  Fixed a bug (#4012) - :doc:`Query Builder <database/query_builder>` methods ``where_in()``, ``or_where_in()``, ``where_not_in()``, ``or_where_not_in()`` didn't take into account previously cached WHERE conditions when query cache is in use.
+-  Fixed a bug (#4015) - :doc:`Email Library <libraries/email>` method ``set_header()`` didn't support method chaining, although it was advertised.
 
 Version 3.0.0
 =============