diff --git a/src/db/db/dbBoxScanner.h b/src/db/db/dbBoxScanner.h
index 7c1a20640..7f5ff0439 100644
--- a/src/db/db/dbBoxScanner.h
+++ b/src/db/db/dbBoxScanner.h
@@ -424,6 +424,7 @@ private:
             for (iterator_type j = c; j < i; ++j) {
               if (bs_boxes_overlap (bc (*i->first), bc (*j->first), enl)) {
                 if (seen.insert (std::make_pair (i->first, j->first)).second) {
+                  seen.insert (std::make_pair (j->first, i->first));
                   rec.add (i->first, i->second, j->first, j->second);
                   if (rec.stop ()) {
                     return false;