diff --git a/time_tracker.module b/time_tracker.module
index 6f8d6ae..6fedf84 100644
--- a/time_tracker.module
+++ b/time_tracker.module
@@ -605,7 +605,12 @@ function time_tracker_nodeapi(&$node, $op) {

     case 'delete':
       db_query("DELETE FROM {time_tracker_entry} WHERE nid = %d", $node->nid);
-      db_query("DELETE FROM {time_tracker_timer} WHERE nid = %d", $node->nid);
+      if (module_exists('time_tracker_timer')) {
+        db_query("DELETE FROM {time_tracker_timer} WHERE nid = %d", $node->nid);
+      }
+      elseif (module_exists('time_estimate') {
+        db_query("DELETE FROM {time_estimate_entry} WHERE nid = %d", $node->nid);
+      }
     break;

     case 'insert':