diff --git a/node_import.inc b/node_import.inc
index 75aba86..a954851 100644
--- a/node_import.inc
+++ b/node_import.inc
@@ -2198,7 +2198,7 @@ function node_import_lock_acquire($release = FALSE) {
     $locked = FALSE;
   }
   else if (!$locked) {
-    if (@db_query("INSERT INTO {variable} (name, value) VALUES ('%s', '%s')", 'node_import:lock', $lock_id)) {
+    if (@db_query("INSERT INTO {variable} (name, value) VALUES ('%s', '%s')", 'node_import:lock', serialize($lock_id))) {
       $locked = TRUE;
     }
   }