diff --git a/src/vs/workbench/api/node/mainThreadEditors.ts b/src/vs/workbench/api/node/mainThreadEditors.ts
index f5a2600054f..34425e2e463 100644
--- a/src/vs/workbench/api/node/mainThreadEditors.ts
+++ b/src/vs/workbench/api/node/mainThreadEditors.ts
@@ -294,6 +294,9 @@ export class MainThreadTextEditor {
 	}
 
 	public matches(editor: IEditor): boolean {
+		if (!editor) {
+			return false;
+		}
 		return editor.getControl() === this._codeEditor;
 	}