diff --git a/src/core/webidl-index.js b/src/core/webidl-index.js
index 5347318018..b55ee3818c 100644
--- a/src/core/webidl-index.js
+++ b/src/core/webidl-index.js
@@ -54,6 +54,10 @@ export function run(conf, doc, cb) {
       collector.appendChild(elem);
       return collector;
     }, pre);
+  // Remove duplicate IDs
+  Array
+    .from(pre.querySelectorAll("*[id]"))
+    .forEach(elem => elem.removeAttribute("id"));
   virtualSummary.appendChild(pre);
   idlIndexSec.appendChild(virtualSummary);
   cb();
diff --git a/tests/spec/core/idl-index-spec.js b/tests/spec/core/idl-index-spec.js
index 55f46492ef..223e831520 100644
--- a/tests/spec/core/idl-index-spec.js
+++ b/tests/spec/core/idl-index-spec.js
@@ -1,6 +1,6 @@
 "use strict";
 describe("Core — IDL Index", () => {
-  afterAll( done => {
+  afterAll(done => {
     flushIframes();
     done();
   });
@@ -64,4 +64,26 @@ interface Bar {
       expect(doc.querySelectorAll("#idl-index > h2").length).toEqual(1);
     }).then(done);
   });
+  it("doesn't include ids in the cloned indexed", done => {
+    const body = `
+      ${makeDefaultBody()}
+      <pre class=idl>
+      interface Test {
+
+      };
+      </pre>
+      <section id="idl-index">
+        <h2>PASS</h2>
+        <p>Custom paragraph.</p>
+      </section>
+    `;
+    var ops = {
+      config: makeBasicConfig(),
+      body,
+    };
+    makeRSDoc(ops, function(doc) {
+      const pre = doc.querySelector("#idl-index pre");
+      expect(pre.querySelectorAll("*[id]").length).toEqual(0);
+    }).then(done);
+  });
 });