diff --git a/libraries/cms/installer/adapter.php b/libraries/cms/installer/adapter.php
index 7e83278af8ad0..e6f423126a99f 100644
--- a/libraries/cms/installer/adapter.php
+++ b/libraries/cms/installer/adapter.php
@@ -564,7 +564,7 @@ protected function getScriptClassName()
 	/**
 	 * Generic install method for extensions
 	 *
-	 * @return  boolean  True on success
+	 * @return  boolean|integer  The extension ID on success, boolean false on failure
 	 *
 	 * @since   3.4
 	 */
@@ -1028,7 +1028,7 @@ protected function triggerManifestScript($method)
 	/**
 	 * Generic update method for extensions
 	 *
-	 * @return  boolean  True on success
+	 * @return  boolean|integer  The extension ID on success, boolean false on failure
 	 *
 	 * @since   3.4
 	 */
diff --git a/libraries/cms/installer/adapter/language.php b/libraries/cms/installer/adapter/language.php
index b719ef4ce5404..db63f82fd3509 100644
--- a/libraries/cms/installer/adapter/language.php
+++ b/libraries/cms/installer/adapter/language.php
@@ -73,7 +73,7 @@ protected function storeExtension()
 	 * the ability to install multiple distinct packs in one install. The
 	 * preferred method is to use a package to install multiple language packs.
 	 *
-	 * @return  boolean  True on success
+	 * @return  boolean|integer  The extension ID on success, boolean false on failure
 	 *
 	 * @since   3.1
 	 */
@@ -131,9 +131,9 @@ public function install()
 	 * @param   integer  $clientId  The client id.
 	 * @param   object   &$element  The XML element.
 	 *
-	 * @return  boolean
+	 * @return  boolean|integer  The extension ID on success, boolean false on failure
 	 *
-	 * @since  3.1
+	 * @since   3.1
 	 */
 	protected function _install($cname, $basePath, $clientId, &$element)
 	{
diff --git a/libraries/cms/installer/adapter/library.php b/libraries/cms/installer/adapter/library.php
index a124903438c03..1f2037a563a8a 100644
--- a/libraries/cms/installer/adapter/library.php
+++ b/libraries/cms/installer/adapter/library.php
@@ -290,7 +290,7 @@ protected function storeExtension()
 	/**
 	 * Custom update method
 	 *
-	 * @return  boolean  True on success
+	 * @return  boolean|integer  The extension ID on success, boolean false on failure
 	 *
 	 * @since   3.1
 	 */