diff --git a/src/headless/public/Terminal.test.ts b/src/headless/public/Terminal.test.ts
index ea77bdeee..289eb72d3 100644
--- a/src/headless/public/Terminal.test.ts
+++ b/src/headless/public/Terminal.test.ts
@@ -400,6 +400,7 @@ describe('Headless API Tests', function (): void {
         originMode: false,
         reverseWraparoundMode: false,
         sendFocusMode: false,
+        synchronizedOutputMode: false,
         wraparoundMode: true
       });
     });