diff --git a/src/core/ClearStack.js b/src/core/ClearStack.js
index c8b2ed21..a9f645ed 100644
--- a/src/core/ClearStack.js
+++ b/src/core/ClearStack.js
@@ -25,6 +25,23 @@ getJasmineRequireObj().clearStack = function(j$) {
   }
 
   function messageChannelImpl(global) {
+    const { setTimeout } = global;
+    const postMessage = getPostMessage(global);
+
+    let currentCallCount = 0;
+    return function clearStack(fn) {
+      currentCallCount++;
+
+      if (currentCallCount < maxInlineCallCount) {
+        postMessage(fn);
+      } else {
+        currentCallCount = 0;
+        setTimeout(fn);
+      }
+    };
+  }
+
+  function getPostMessage(global) {
     const { MessageChannel, setTimeout } = global;
     const channel = new MessageChannel();
     let head = {};
@@ -48,17 +65,9 @@ getJasmineRequireObj().clearStack = function(j$) {
       }
     };
 
-    let currentCallCount = 0;
-    return function clearStack(fn) {
-      currentCallCount++;
-
-      if (currentCallCount < maxInlineCallCount) {
-        tail = tail.next = { task: fn };
-        channel.port2.postMessage(0);
-      } else {
-        currentCallCount = 0;
-        setTimeout(fn);
-      }
+    return function postMessage(fn) {
+      tail = tail.next = { task: fn };
+      channel.port2.postMessage(0);
     };
   }