diff --git a/src/browser/TestUtils.test.ts b/src/browser/TestUtils.test.ts
index 1a29c186..61b6c0d7 100644
--- a/src/browser/TestUtils.test.ts
+++ b/src/browser/TestUtils.test.ts
@@ -257,6 +257,9 @@ export class MockBuffer implements IBuffer {
   public getWhitespaceCell(attr?: IAttributeData): ICellData {
     throw new Error('Method not implemented.');
   }
+  public clearMarkers(): void {
+    throw new Error('Method not implemented.');
+  }
 }
 
 export class MockRenderer implements IRenderer {