diff --git a/node_import.inc b/node_import.inc
index 6389f6e..931db28 100644
--- a/node_import.inc
+++ b/node_import.inc
@@ -2184,22 +2184,24 @@ function node_import_drupal_validate_form($form_id, $form, &$form_state) {
  *   Boolean. Whether the lock was acquired.
  */
 function node_import_lock_acquire($release = FALSE) {
-  static $lock_id, $locked;
+  $lock_id = variable_get('node_import:lock', '');
+  $locked = variable_get('node_import:locked', FALSE);
 
-  if (!isset($lock_id)) {
+  if (empty($lock_id)) {
     $lock_id = md5(uniqid());
     $locked = FALSE;
     register_shutdown_function('node_import_lock_release');
   }
 
   if ($release) {
-    db_query("DELETE FROM {variable} WHERE name = '%s'", 'node_import:lock');
+    variable_set('node_import:lock', '');
+    variable_set('node_import:locked', FALSE);
     $locked = FALSE;
   }
   else if (!$locked) {
-    if (@db_query("INSERT INTO {variable} (name, value) VALUES ('%s', '%s')", 'node_import:lock', $lock_id)) {
-      $locked = TRUE;
-    }
+    variable_set('node_import:lock', $lock_id);
+    variable_set('node_import:locked', TRUE);
+    $locked = TRUE;
   }
 
   return $locked;