diff --git a/app/javascript/new_design/dossiers/auto-uploads-controllers.js b/app/javascript/new_design/dossiers/auto-uploads-controllers.js
index ad68b081d..90348566b 100644
--- a/app/javascript/new_design/dossiers/auto-uploads-controllers.js
+++ b/app/javascript/new_design/dossiers/auto-uploads-controllers.js
@@ -1,7 +1,13 @@
 import Rails from '@rails/ujs';
 import AutoUploadController from './auto-upload-controller.js';
+import { fire } from '@utils';
 import { FAILURE_CONNECTIVITY } from '../../shared/activestorage/file-upload-error';
 
+//
+// DEBUG
+//
+const originalImpl = FileReader.prototype.addEventListener;
+
 // Manage multiple concurrent uploads.
 //
 // When the first upload starts, all the form "Submit" buttons are disabled.
@@ -36,6 +42,25 @@ export default class AutoUploadsControllers {
         .querySelectorAll('button[type=submit]')
         .forEach(submitButton => Rails.disableElement(submitButton));
     }
+
+    //
+    // DEBUG: hook into FileReader onload event
+    //
+    if (FileReader.prototype.addEventListener === originalImpl) {
+      FileReader.prototype.addEventListener = function() {
+        // When DirectUploads attempts to add an event listener for "error",
+        // also insert a custom event listener of our that will report errors to Sentry.
+        if (arguments[0] == 'error') {
+          let handler = event => {
+            let message = `FileReader ${event.target.error.name}: ${event.target.error.message}`;
+            fire(document, 'sentry:capture-exception', new Error(message));
+          };
+          originalImpl.apply(this, ['error', handler]);
+        }
+        // Add the originally requested event listener
+        return originalImpl.apply(this, arguments);
+      };
+    }
   }
 
   _decrementInFlightUploads(form) {
@@ -48,5 +73,12 @@ export default class AutoUploadsControllers {
         .querySelectorAll('button[type=submit]')
         .forEach(submitButton => Rails.enableElement(submitButton));
     }
+
+    //
+    // DEBUG: remove the FileReader hook we set before.
+    //
+    if (this.inFlightUploadsCount == 0) {
+      FileReader.prototype.addEventListener = originalImpl;
+    }
   }
 }