diff --git a/types/chart.js/index.d.ts b/types/chart.js/index.d.ts
index 614fbe26ef..6a59e19ffb 100644
--- a/types/chart.js/index.d.ts
+++ b/types/chart.js/index.d.ts
@@ -39,7 +39,8 @@ declare class Chart {
     };
 }
 declare class PluginServiceStatic {
-    register(plugin?: PluginServiceRegistrationOptions): void;
+    register(plugin: PluginServiceRegistrationOptions): void;
+    unregister(plugin: PluginServiceRegistrationOptions): void;
 }
 
 interface PluginServiceRegistrationOptions {