diff --git a/src/Plugin/PluginAccess.php b/src/Plugin/PluginAccess.php
index 3bc0e5b8dec645edd1e7a148721ec2321014345b..e0c1c1bb7d4107845019223393f84341ed96764d 100644
--- a/src/Plugin/PluginAccess.php
+++ b/src/Plugin/PluginAccess.php
@@ -15,7 +15,7 @@ trait PluginAccess {
 	 *
 	 * @param AbstractPlugin $plugin Plugin.
 	 */
-	public function set_plugin( $plugin ) {
+	public function set_plugin( AbstractPlugin $plugin ) {
 		$this->plugin = $plugin;
 	}