diff --git a/src/styles/respec.css.js b/src/styles/respec.css.js
index 09ac3b78c1..52dc162eb8 100644
--- a/src/styles/respec.css.js
+++ b/src/styles/respec.css.js
@@ -138,6 +138,7 @@ aside.example .marker > a.self-link {
 .header-wrapper {
   display: flex;
   align-items: baseline;
+  width: 100%;
 }
 
 :is(h2, h3, h4, h5, h6):not(#toc > h2, #abstract > h2, #sotd > h2, .head > h2):has(+ a.self-link) {
diff --git a/tests/spec/core/style-spec.js b/tests/spec/core/style-spec.js
index 06048ac159..004f6502b0 100644
--- a/tests/spec/core/style-spec.js
+++ b/tests/spec/core/style-spec.js
@@ -1,4 +1,5 @@
 import { flushIframes, makeRSDoc, makeStandardOps } from "../SpecHelper.js";
+import respecCss from "../../../src/styles/respec.css.js";
 
 describe("Core — Style", () => {
   afterAll(flushIframes);
@@ -7,4 +8,10 @@ describe("Core — Style", () => {
     const style = doc.getElementById("respec-mainstyle");
     expect(style).toBeTruthy();
   });
+
+  it("makes header wrapper full width", () => {
+    expect(respecCss).toMatch(
+      /\.header-wrapper\s*\{[^}]*\bwidth:\s*100%\s*;[^}]*\}/
+    );
+  });
 });