diff --git a/includes/common.inc b/includes/common.inc
index f6171cf..fea09a6 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -3878,7 +3878,16 @@ function drupal_html_id($id) {
       // requested id. $_POST['ajax_html_ids'] contains the ids as they were
       // returned by this function, potentially with the appended counter, so
       // we parse that to reconstruct the $seen_ids array.
-      foreach ($_POST['ajax_html_ids'] as $seen_id) {
+      if (is_array($_POST['ajax_html_ids'])) {
+        $ajax_html_ids = $_POST['ajax_html_ids'];
+      }
+      else {
+        // jquery.form.js may send the server a comma-separated string instead
+        // of an array(see http://drupal.org/node/1575060), so we need to
+        // convert it to an array in that case.
+        $ajax_html_ids = explode(',', $_POST['ajax_html_ids']);
+      }
+      foreach ($ajax_html_ids as $seen_id) {
         // We rely on '--' being used solely for separating a base id from the
         // counter, which this function ensures when returning an id.
         $parts = explode('--', $seen_id, 2);