Index: xmlsitemap.module
===================================================================
--- xmlsitemap.module	(revision 5970)
+++ xmlsitemap.module	(working copy)
@@ -438,7 +438,7 @@
 
   if (!empty($smids)) {
     $sitemaps = xmlsitemap_sitemap_load_multiple($smids);
-    db_query("DELETE FROM {xmlsitemap_sitemap} WHERE smid IN (" . db_placeholders($smids) . ")", $smids);
+    db_query("DELETE FROM {xmlsitemap_sitemap} WHERE smid IN (" . db_placeholders($smids, 'varchar') . ")", $smids);
 
     foreach ($sitemaps as $sitemap) {
       xmlsitemap_clear_directory($sitemap, TRUE);