diff --git a/src/slicer.js b/src/slicer.js
index ead168b..5341d9f 100644
--- a/src/slicer.js
+++ b/src/slicer.js
@@ -63,10 +63,10 @@ function sliceAsync(settings, geometry, openObjectIndexes, constructLinePreview,
     // create the slicer worker
     const slicerWorker = new SlicerWorker();
 
-    slicerWorker.onerror = error => {
+    slicerWorker.addEventListener('error', event => {
       slicerWorker.terminate();
-      reject(error);
-    };
+      reject(event);
+    });
 
     // listen to messages send from worker
     slicerWorker.addEventListener('message', (event) => {
diff --git a/src/slicer.worker.js b/src/slicer.worker.js
index 0168b7b..2d866ef 100644
--- a/src/slicer.worker.js
+++ b/src/slicer.worker.js
@@ -12,7 +12,7 @@ const onProgress = progress => {
 
 const loader = new JSONLoader();
 
-self.addEventListener('message', async (event) => {
+self.addEventListener('message', (event) => {
   const { message, data } = event.data;
   switch (message) {
     case 'SLICE': {