diff --git a/src/core/title.js b/src/core/title.js
index 912df79c35..9d2c2b7b4e 100644
--- a/src/core/title.js
+++ b/src/core/title.js
@@ -51,7 +51,18 @@ export function run(conf) {
   }
 
   // Decorate the spec title
-  if (!h1Elem.id) h1Elem.id = "title";
+  if (!h1Elem.id) {
+    const existing = document.getElementById("title");
+    if (existing && existing !== h1Elem) {
+      const msg =
+        'Another element already uses `id="title"`. ' +
+        "The spec's `<h1>` will use a different id to avoid a collision.";
+      showError(msg, name, { elements: [existing] });
+      h1Elem.id = "document-title";
+    } else {
+      h1Elem.id = "title";
+    }
+  }
   h1Elem.classList.add("title");
 
   setDocumentTitle(conf, h1Elem);