diff --git a/includes/datastream.inc b/includes/datastream.inc
index edc8ceb1..592870b7 100644
--- a/includes/datastream.inc
+++ b/includes/datastream.inc
@@ -30,6 +30,7 @@ function islandora_download_datastream(AbstractDatastream $datastream) {
  *   The version of the datastream to display
  */
 function islandora_view_datastream(AbstractDatastream $datastream, $download = FALSE, $version = NULL) {
+  module_load_include('inc', 'islandora', 'includes/mimetype.utils');
   // XXX: Certain features of the Devel module rely on the use of "shutdown
   // handlers", such as query logging... The problem is that they might blindly
   // add additional output which will break things if what is actually being
@@ -45,7 +46,6 @@ function islandora_view_datastream(AbstractDatastream $datastream, $download = F
       return drupal_not_found();
     }
   }
-
   header('Content-type: ' . $datastream->mimetype);
   if ($datastream->controlGroup == 'M' || $datastream->controlGroup == 'X') {
     header('Content-length: ' . $datastream->size);
@@ -53,7 +53,7 @@ function islandora_view_datastream(AbstractDatastream $datastream, $download = F
   if ($download) {
     // Browsers will not append all extensions.
     $mime_detect = new MimeDetect();
-    $extension = '.' . $mime_detect->getExtension($datastream->mimetype);
+    $extension = '.' . islandora_get_extension_for_mimetype($datastream->mimetype);
     // Prevent adding on a duplicate extension.
     $label = $datastream->label;
     $extension_length = strlen($extension);
diff --git a/includes/mime_detect.inc b/includes/mime_detect.inc
index 29fcf1e5..da2c69f3 100644
--- a/includes/mime_detect.inc
+++ b/includes/mime_detect.inc
@@ -134,7 +134,6 @@ class MimeDetect {
     'xhtml' => 'application/xhtml+xml',
     'xsl' => 'text/xsl',
     'xslt' => 'text/xsl',
-    'xml' => 'application/xml',
     'csv' => 'text/csv',
     'tsv' => 'text/tab-separated-values',
     'txt' => 'text/plain',
diff --git a/includes/mimetype.utils.inc b/includes/mimetype.utils.inc
new file mode 100644
index 00000000..989c55cd
--- /dev/null
+++ b/includes/mimetype.utils.inc
@@ -0,0 +1,31 @@
+<?php
+/**
+ * @file
+ * Mimetype specific utility functions.
+ */
+
+/**
+ * Retrieve the correct file extension for a give mimetype.
+ *
+ * @param string $mimetype
+ *   The mimetype whose extension is required.
+ *
+ * @return string
+ *   The extension mapped to the given mimetype.
+ */
+function islandora_get_extension_for_mimetype($mimetype) {
+  // file.mimetypes.inc is a part of Drupal core, however is not
+  // automatically loaded. Manually require it.
+  require_once DRUPAL_ROOT . "/includes/file.mimetypes.inc";
+
+  $mimetype_mapping = file_mimetype_mapping();
+  $extension_index = array_search($mimetype, $mimetype_mapping['mimetypes']);
+  $mime_array_flipped = array_reverse($mimetype_mapping['extensions']);
+  $extension = array_search($extension_index, $mime_array_flipped);
+
+  // We can only have one mapping in drupal for 'xml'.
+  if ($mimetype == "text/xml") {
+    return "xml";
+  }
+  return $extension;
+}
diff --git a/islandora.module b/islandora.module
index b2bb99b8..c930ba5f 100644
--- a/islandora.module
+++ b/islandora.module
@@ -1590,6 +1590,7 @@ function islandora_download_clip(AbstractObject $object) {
 function islandora_file_mimetype_mapping_alter(&$mapping) {
   $mime_detect = new MimeDetect();
   $types = $mime_detect->getMimeTypes();
+
   $diff = array_diff_key($types, $mapping['extensions']);
   foreach ($diff as $ext => $mime) {
     $mapping['mimetypes'][] = $mime;