diff --git a/core/misc/autocomplete.js b/core/misc/autocomplete.js
index 2f4e5f69935..122f05d7e22 100644
--- a/core/misc/autocomplete.js
+++ b/core/misc/autocomplete.js
@@ -293,10 +293,11 @@ Drupal.ACDB.prototype.search = function (searchString) {
   this.timer = setTimeout(function () {
     db.owner.setStatus('begin');
 
-    // Ajax GET request for autocompletion.
+    // Ajax GET request for autocompletion. We use Drupal.encodePath instead of
+    // encodeURIComponent to allow autocomplete search terms to contain slashes.
     $.ajax({
       type: 'GET',
-      url: db.uri + '/' + encodeURIComponent(searchString),
+      url: db.uri + '/' + Drupal.encodePath(searchString),
       dataType: 'json',
       success: function (matches) {
         if (typeof matches.status === 'undefined' || matches.status !== 0) {
diff --git a/core/modules/taxonomy/taxonomy.pages.inc b/core/modules/taxonomy/taxonomy.pages.inc
index 4bdcbc5141f..6994b6edfce 100644
--- a/core/modules/taxonomy/taxonomy.pages.inc
+++ b/core/modules/taxonomy/taxonomy.pages.inc
@@ -106,6 +106,13 @@ function taxonomy_term_feed($term) {
  * @see taxonomy_field_widget_info()
  */
 function taxonomy_autocomplete($field_name, $tags_typed = '') {
+  // If the request has a '/' in the search text, then the menu system will have
+  // split it into multiple arguments, recover the intended $tags_typed.
+  $args = func_get_args();
+  // Shift off the $field_name argument.
+  array_shift($args);
+  $tags_typed = implode('/', $args);
+
   // Make sure the field exists and is a taxonomy field.
   if (!($field = field_info_field($field_name)) || $field['type'] !== 'taxonomy_term_reference') {
     // Error string. The JavaScript handler will realize this is not JSON and
diff --git a/core/modules/taxonomy/taxonomy.test b/core/modules/taxonomy/taxonomy.test
index f8f7ed867f1..de50f2a9448 100644
--- a/core/modules/taxonomy/taxonomy.test
+++ b/core/modules/taxonomy/taxonomy.test
@@ -731,6 +731,58 @@ class TaxonomyTermTestCase extends TaxonomyWebTestCase {
      $this->assertRaw($message, t('Autocomplete returns correct error message when the taxonomy field does not exist.'));
   }
 
+  /**
+   * Tests term autocompletion edge cases with slashes in the names.
+   */
+  function testTermAutocompletion() {
+    // Add a term with a slash in the name.
+    $first_term = $this->createTerm($this->vocabulary);
+    $first_term->name = '10/16/2011';
+    taxonomy_term_save($first_term);
+    // Add another term that differs after the slash character.
+    $second_term = $this->createTerm($this->vocabulary);
+    $second_term->name = '10/17/2011';
+    taxonomy_term_save($second_term);
+    // Add another term that has both a comma and a slash character.
+    $third_term = $this->createTerm($this->vocabulary);
+    $third_term->name = 'term with, a comma and / a slash';
+    taxonomy_term_save($third_term);
+
+    // Try to autocomplete a term name that matches both terms.
+    // We should get both term in a json encoded string.
+    $input = '10/';
+    $path = 'taxonomy/autocomplete/taxonomy_';
+    $path .= $this->vocabulary->machine_name . '/' . $input;
+    // The result order is not guaranteed, so check each term separately.
+    $url = url($path, array('absolute' => TRUE));
+    $result = drupal_http_request($url);
+    $data = drupal_json_decode($result->data);
+    $this->assertEqual($data[$first_term->name], check_plain($first_term->name), 'Autocomplete returned the first matching term');
+    $this->assertEqual($data[$second_term->name], check_plain($second_term->name), 'Autocomplete returned the second matching term');
+
+    // Try to autocomplete a term name that matches first term.
+    // We should only get the first term in a json encoded string.
+    $input = '10/16';
+    $url = 'taxonomy/autocomplete/taxonomy_';
+    $url .= $this->vocabulary->machine_name . '/' . $input;
+    $this->drupalGet($url);
+    $target = array($first_term->name => check_plain($first_term->name));
+    $this->assertRaw(drupal_json_encode($target), 'Autocomplete returns only the expected matching term.');
+
+    // Try to autocomplete a term name with both a comma and a slash.
+    $input = '"term with, comma and / a';
+    $url = 'taxonomy/autocomplete/taxonomy_';
+    $url .= $this->vocabulary->machine_name . '/' . $input;
+    $this->drupalGet($url);
+    $n = $third_term->name;
+    // Term names containing commas or quotes must be wrapped in quotes.
+    if (strpos($third_term->name, ',') !== FALSE || strpos($third_term->name, '"') !== FALSE) {
+      $n = '"' . str_replace('"', '""', $third_term->name) . '"';
+    }
+    $target = array($n => check_plain($third_term->name));
+    $this->assertRaw(drupal_json_encode($target), 'Autocomplete returns a term containing a comma and a slash.');
+  }
+
   /**
    * Save, edit and delete a term using the user interface.
    */