diff --git a/src/lib/libpthread.js b/src/lib/libpthread.js
index 718b0bc5ff7e0..d3f367042bb1a 100644
--- a/src/lib/libpthread.js
+++ b/src/lib/libpthread.js
@@ -275,7 +275,7 @@ var LibraryPThread = {
     //                    ready to host pthreads.
     loadWasmModuleToWorker: (worker) => new Promise((onFinishedLoading) => {
       worker.onmessage = (e) => {
-        var d = e['data'];
+        var d = e.data;
         var cmd = d.cmd;
 #if PTHREADS_DEBUG
         dbg(`main thread: received message '${cmd}' from worker. ${d}`);
@@ -440,7 +440,7 @@ var LibraryPThread = {
         sharedModules,
 #endif
 #if ASSERTIONS
-        'workerID': worker.workerID,
+        workerID: worker.workerID,
 #endif
       });
     }),
@@ -597,7 +597,7 @@ var LibraryPThread = {
     // the onmessage handlers if the message was coming from a valid worker.
     worker.onmessage = (e) => {
 #if ASSERTIONS
-      var cmd = e['data'].cmd;
+      var cmd = e.data.cmd;
       err(`received "${cmd}" command from terminated worker: ${worker.workerID}`);
 #endif
     };
diff --git a/src/runtime_pthread.js b/src/runtime_pthread.js
index dbcb641344523..de70f2460d5c9 100644
--- a/src/runtime_pthread.js
+++ b/src/runtime_pthread.js
@@ -44,7 +44,7 @@ if (ENVIRONMENT_IS_PTHREAD) {
 
   {{{ asyncIf(ASYNCIFY == 2) }}}function handleMessage(e) {
     try {
-      var msgData = e['data'];
+      var msgData = e.data;
       //dbg('msgData: ' + Object.keys(msgData));
       var cmd = msgData.cmd;
       if (cmd == {{{ CMD_LOAD }}}) { // Preload command that is called once per worker to parse and load the Emscripten code.