diff --git a/toolkit/devtools/server/tests/mochitest/chrome.ini b/toolkit/devtools/server/tests/mochitest/chrome.ini
index 30ade2d2d88a..804bb3785967 100644
--- a/toolkit/devtools/server/tests/mochitest/chrome.ini
+++ b/toolkit/devtools/server/tests/mochitest/chrome.ini
@@ -78,6 +78,7 @@ skip-if = buildapp == 'mulet'
 [test_memory_allocations_04.html]
 [test_memory_allocations_05.html]
 [test_memory_allocations_06.html]
+[test_memory_allocations_07.html]
 [test_memory_attach_01.html]
 [test_memory_attach_02.html]
 [test_memory_census.html]
diff --git a/toolkit/devtools/server/tests/mochitest/test_memory_allocations_07.html b/toolkit/devtools/server/tests/mochitest/test_memory_allocations_07.html
new file mode 100644
index 000000000000..c26c2d8ecbb9
--- /dev/null
+++ b/toolkit/devtools/server/tests/mochitest/test_memory_allocations_07.html
@@ -0,0 +1,55 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+Bug 1192335 - Test getting the byte sizes for allocations.
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Memory monitoring actor test</title>
+  <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css">
+</head>
+<body>
+<pre id="test">
+<script src="memory-helpers.js" type="application/javascript;version=1.8"></script>
+<script>
+window.onload = function() {
+  SimpleTest.waitForExplicitFinish();
+
+  Task.spawn(function* () {
+    var { memory, client } = yield startServerAndGetSelectedTabMemory();
+    yield memory.attach();
+
+    var allocs = [];
+    function allocator() {
+      allocs.push(new Object);
+    }
+
+    yield memory.startRecordingAllocations();
+
+    allocator();
+    allocator();
+    allocator();
+
+    var response = yield memory.getAllocations();
+    yield memory.stopRecordingAllocations();
+
+    ok(response.allocationSizes, "The response should have bytesizes.");
+    is(response.allocationSizes.length, response.allocations.length,
+       "There should be a bytesize for every allocation.");
+    ok(response.allocationSizes.length >= 3,
+       "There are atleast 3 allocations.");
+    ok(response.allocationSizes.every(isPositiveNumber), "every bytesize is a positive number");
+
+    yield memory.detach();
+    destroyServerAndFinish(client);
+  });
+};
+
+function isPositiveNumber (n) {
+  return typeof n === "number" && n > 0;
+}
+</script>
+</pre>
+</body>
+</html>
diff --git a/toolkit/devtools/shared/memory.js b/toolkit/devtools/shared/memory.js
index 508accb877ae..fe7d28fe66f0 100644
--- a/toolkit/devtools/shared/memory.js
+++ b/toolkit/devtools/shared/memory.js
@@ -226,6 +226,11 @@ let Memory = exports.Memory = Class({
    *                <timestamp for allocations[1]>,
    *                ...
    *              ],
+   *              allocationSizes: [
+   *                <bytesize for allocations[0]>,
+   *                <bytesize for allocations[1]>,
+   *                ...
+   *              ],
    *              frames: [
    *                {
    *                  line: <line number for this frame>,
@@ -275,8 +280,9 @@ let Memory = exports.Memory = Class({
     const packet = {
       allocations: [],
       allocationsTimestamps: [],
+      allocationSizes: [],
     };
-    for (let { frame: stack, timestamp } of allocations) {
+    for (let { frame: stack, timestamp, size } of allocations) {
       if (stack && Cu.isDeadWrapper(stack)) {
         continue;
       }
@@ -284,7 +290,7 @@ let Memory = exports.Memory = Class({
       // Safe because SavedFrames are frozen/immutable.
       let waived = Cu.waiveXrays(stack);
 
-      // Ensure that we have a form, count, and index for new allocations
+      // Ensure that we have a form, size, and index for new allocations
       // because we potentially haven't seen some or all of them yet. After this
       // loop, we can rely on the fact that every frame we deal with already has
       // its metadata stored.
@@ -292,6 +298,7 @@ let Memory = exports.Memory = Class({
 
       packet.allocations.push(index);
       packet.allocationsTimestamps.push(timestamp);
+      packet.allocationSizes.push(size);
     }
 
     return this._frameCache.updateFramePacket(packet);
