diff --git a/Source/WebInspectorUI/ChangeLog b/Source/WebInspectorUI/ChangeLog
index 6ca5261df790..7bc79245d606 100644
--- a/Source/WebInspectorUI/ChangeLog
+++ b/Source/WebInspectorUI/ChangeLog
@@ -1,3 +1,14 @@
+2017-09-08  Joseph Pecoraro  <pecoraro@apple.com>
+
+        Uncaught Exception: TypeError: this._heapSnapshot.addEventListener is not a function.
+        https://bugs.webkit.org/show_bug.cgi?id=176633
+
+        Reviewed by Michael Saboff.
+
+        * UserInterface/Proxies/HeapSnapshotDiffProxy.js:
+        (WI.HeapSnapshotDiffProxy):
+        This class has listeners of another object's events. It should extend WI.Object.
+
 2017-08-14  Simon Fraser  <simon.fraser@apple.com>
 
         Remove Proximity Events and related code
diff --git a/Source/WebInspectorUI/UserInterface/Proxies/HeapSnapshotDiffProxy.js b/Source/WebInspectorUI/UserInterface/Proxies/HeapSnapshotDiffProxy.js
index 7d07ef99f9d9..c1c544656014 100644
--- a/Source/WebInspectorUI/UserInterface/Proxies/HeapSnapshotDiffProxy.js
+++ b/Source/WebInspectorUI/UserInterface/Proxies/HeapSnapshotDiffProxy.js
@@ -23,10 +23,12 @@
  * THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-WI.HeapSnapshotDiffProxy = class HeapSnapshotDiffProxy
+WI.HeapSnapshotDiffProxy = class HeapSnapshotDiffProxy extends WI.Object
 {
     constructor(snapshotDiffObjectId, snapshot1, snapshot2, totalSize, totalObjectCount, categories)
     {
+        super();
+
         this._proxyObjectId = snapshotDiffObjectId;
 
         console.assert(snapshot1 instanceof WI.HeapSnapshotProxy);