diff --git a/client/src/components/lanes/__tests__/DiffEditor.test.tsx b/client/src/components/lanes/__tests__/DiffEditor.test.tsx
index 6d3a58ee..87656f95 100644
--- a/client/src/components/lanes/__tests__/DiffEditor.test.tsx
+++ b/client/src/components/lanes/__tests__/DiffEditor.test.tsx
@@ -66,7 +66,10 @@ describe("DiffEditor", () => {
     expect(right).toHaveAttribute("contenteditable", "true");
     expect(container.querySelector(".cm-merge-a .cm-changedLine.cm-ah-mod")).not.toBeNull();
     expect(container.querySelector(".cm-merge-b .cm-changedLine.cm-ah-mod")).not.toBeNull();
-    expect(container.querySelector(".cm-merge-revert button")).toHaveAttribute("title", "Revert");
+    // The revert column is drawn in CodeMirror's next measure pass, not at mount.
+    await waitFor(() =>
+      expect(container.querySelector(".cm-merge-revert button")).toHaveAttribute("title", "Revert")
+    );
   });
 
   it("folds unchanged lines away when collapsed, and offers Revert on a block", async () => {