typo correct aria-controls

docs/4.0/components/collapse.md

@@ -40,7 +40,7 @@ Multiple `<button>` or `<a>` can  show and hide an element if they each referenc
 {% example html %}
 <p>
   <a class="btn btn-primary" data-toggle="collapse" href="#multiCollapseExample1" aria-expanded="false" aria-controls="multiCollapseExample1">Toggle first element</a>
-  <button class="btn btn-primary" type="button" data-toggle="collapse" data-target="#multiCollapseExample2" aria-expanded="false" aria-controls="multiCollapseExample1">Toggle second element</button>
+  <button class="btn btn-primary" type="button" data-toggle="collapse" data-target="#multiCollapseExample2" aria-expanded="false" aria-controls="multiCollapseExample2">Toggle second element</button>
   <button class="btn btn-primary" type="button" data-toggle="collapse" data-target=".multi-collapse" aria-expanded="false" aria-controls="multiCollapseExample1 multiCollapseExample2">Toggle both elements</button>
 </p>
 <div class="row">