diff --git a/ace.d.ts b/ace.d.ts
index e816e36e72b..58276a1e988 100644
--- a/ace.d.ts
+++ b/ace.d.ts
@@ -792,6 +792,7 @@ export namespace Ace {
     on(name: 'mouseup', callback: (e: any) => void): void;
     on(name: 'mousewheel', callback: (e: any) => void): void;
     on(name: 'click', callback: (e: any) => void): void;
+    on(name: 'guttermousedown', callback: (e: any) => void): void;
 
     onPaste(text: string, event: any): void;