diff --git a/includes/add_datastream.form.inc b/includes/add_datastream.form.inc
index 40e1537d..4484a903 100644
--- a/includes/add_datastream.form.inc
+++ b/includes/add_datastream.form.inc
@@ -149,7 +149,8 @@ function islandora_add_datastream_form_validate(array $form, array &$form_state)
     $form_state['values']['dsid']
   );
   $file = file_load($form_state['values']['file']);
-  if ($file) {
+  // Only validate extensions if mimes defined in ds-composite.
+  if ($file && $extensions) {
     $errors = file_validate_extensions($file, implode(' ', $extensions));
     if (count($errors) > 0) {
       form_set_error(
diff --git a/includes/mimetype.utils.inc b/includes/mimetype.utils.inc
index beb4dfef..03708f99 100644
--- a/includes/mimetype.utils.inc
+++ b/includes/mimetype.utils.inc
@@ -73,7 +73,7 @@ function islandora_get_extensions_for_mimetype($mimetype) {
 function islandora_get_extensions_for_datastream(AbstractObject $object, $dsid) {
   module_load_include('inc', 'islandora', 'includes/utilities');
   $datastream_mime_map = islandora_get_datastreams_requirements_from_models($object->models);
-  $mimes = $datastream_mime_map[$dsid]['mime'];
+  $mimes = isset($datastream_mime_map[$dsid]) ? $datastream_mime_map[$dsid]['mime'] : array();
   if (isset($object[$dsid])) {
     $current_mime = $object[$dsid]->mimetype;
     if (!in_array($current_mime, $mimes)) {
@@ -84,5 +84,5 @@ function islandora_get_extensions_for_datastream(AbstractObject $object, $dsid)
   foreach ($mimes as $mime) {
     $extensions = array_merge($extensions, islandora_get_extensions_for_mimetype($mime));
   }
-  return $extensions;
+  return array_unique($extensions);
 }