diff --git a/plupload.js b/plupload.js
index f8be4d1..d98f3ac 100644
--- a/plupload.js
+++ b/plupload.js
@@ -58,11 +58,10 @@ Drupal.behaviors.plupload = {
       $form.submit(function(e) {
         var uploader = $('.plupload-element', this).pluploadQueue();
 
-        // Only allow the submit to proceed if there are files and they've all
-        // completed uploading.
-        // @todo Implement a setting for whether the field is required, rather
-        //   than assuming that all are.
-        if (uploader.files.length > 0 && uploader.total.uploaded == uploader.files.length) {
+        // Allow the submit to proceed if there are files and they've all
+        // completed uploading, or if there are no files and the field is not
+        // required.
+        if ((uploader.files.length > 0 && uploader.total.uploaded == uploader.files.length) || (uploader.files.length == 0 && !pluploadSettings.required)) {
           // Plupload's html4 runtime has a bug where it changes the attributes
           // of the form to handle the file upload, but then fails to change
           // them back after the upload is finished.
diff --git a/plupload.module b/plupload.module
index a37a62a..42ac5d0 100644
--- a/plupload.module
+++ b/plupload.module
@@ -220,6 +220,8 @@ function plupload_element_pre_render($element) {
     );
   }
 
+  $settings['required'] = !empty($element['#required']);
+
   if (empty($element['#description'])) {
     $element['#description'] = '';
   }