diff --git a/plupload.js b/plupload.js
index f8be4d1..4078eeb 100644
--- a/plupload.js
+++ b/plupload.js
@@ -56,13 +56,28 @@ Drupal.behaviors.plupload = {
         'target': $form.attr('target')
       };
       $form.submit(function(e) {
-        var uploader = $('.plupload-element', this).pluploadQueue();
+        var uploader = $('#'+id).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) {
+        // Handle file required setting.
+        if (uploader.files.length == 0) {
+          if (!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.
+            for (var attr in originalFormAttributes) {
+              $form.attr(attr, originalFormAttributes[attr]);
+            }
+            return;
+          }
+          else {
+            e.preventDefault();
+            var label = $('label.'+id).text();
+            alert(Drupal.t('You must at least upload one file to !label.', {'!label': label.substring(0, label.length-2)}));
+          }
+        }
+
+        // Check if uploaded is completed
+        if (uploader.total.uploaded == uploader.files.length) {
           // Plupload's html4 runtime has a bug where it changes the attributes
           // of the form to handle the file upload, but then fails to change
           // them back after the upload is finished.
@@ -71,19 +86,14 @@ Drupal.behaviors.plupload = {
           }
           return;
         }
-
-        // If we're here, stop the form submit, and perform logic as appropriate
-        // to the current upload state.
-        e.preventDefault();
-        if (uploader.files.length == 0) {
-          alert('You must at least upload one file.');
-        }
         else if (uploader.state == plupload.STARTED) {
-          alert('Your files are currently being uploaded. Please wait until they are finished before submitting this form.');
+          e.preventDefault();
+          alert(Drupal.t('Your files are currently being uploaded. Please wait until they are finished before submitting this form.'));
         }
         else {
           var stateChangedHandler = function() {
             if (uploader.total.uploaded == uploader.files.length) {
+              e.preventDefault();
               // Plupload's html4 runtime has a bug where it changes the
               // attributes of the form to handle the file upload, but then
               // fails to change them back after the upload is finished.
diff --git a/plupload.module b/plupload.module
index a37a62a..814dc80 100644
--- a/plupload.module
+++ b/plupload.module
@@ -225,6 +225,8 @@ function plupload_element_pre_render($element) {
   }
   $element['#description'] = theme('file_upload_help', array('description' => $element['#description'], 'upload_validators' => $element['#upload_validators']));
 
+  $settings['required'] = $element['#required'];
+
   $element['#attached']['js'][] = array(
     'type' => 'setting',
     'data' => array('plupload' => array($element['#id'] => $settings)),