Index: xmlsitemap_node/xmlsitemap_node.module
===================================================================
--- xmlsitemap_node/xmlsitemap_node.module	(revision 1593)
+++ xmlsitemap_node/xmlsitemap_node.module	(working copy)
@@ -195,6 +195,12 @@
 
   if (!isset($timestamps[$node->nid])) {
     $timestamps[$node->nid] = array();
+    if (module_exists('comment')) {
+        $query = db_query("SELECT c.timestamp FROM {comments} c WHERE c.nid = %d AND c.status = %d UNION ALL SELECT nr.timestamp FROM {node_revisions} nr WHERE nr.nid = %d", $node->nid, COMMENT_PUBLISHED, $node->nid);
+    }
+    else {
+        $query = db_query("SELECT nr.timestamp FROM {node_revisions} nr WHERE nr.nid = %d", $node->nid); 
+    }
-    $query = db_query("SELECT c.timestamp FROM {comments} c WHERE c.nid = %d AND c.status = %d UNION ALL SELECT nr.timestamp FROM {node_revisions} nr WHERE nr.nid = %d", $node->nid, COMMENT_PUBLISHED, $node->nid);
     while ($timestamp = db_result($query)) {
       $timestamps[$node->nid][] = (int) $timestamp;