diff --git a/src/db/db/dbAsIfFlatRegion.cc b/src/db/db/dbAsIfFlatRegion.cc
index 03a5e4e29..0cbd29585 100644
--- a/src/db/db/dbAsIfFlatRegion.cc
+++ b/src/db/db/dbAsIfFlatRegion.cc
@@ -1030,7 +1030,7 @@ AsIfFlatRegion::run_check (db::edge_relation_type rel, bool different_polygons,
   check.set_min_projection (min_projection);
   check.set_max_projection (max_projection);
 
-  db::check_local_operation<db::Polygon, db::Polygon, db::EdgePair> op (check, different_polygons, other != 0, other->is_merged (), shielded);
+  db::check_local_operation<db::Polygon, db::Polygon, db::EdgePair> op (check, different_polygons, other != 0, other && other->is_merged (), shielded);
 
   db::local_processor<db::Polygon, db::Polygon, db::EdgePair> proc;
   proc.set_base_verbosity (base_verbosity ());
diff --git a/src/db/db/dbDeepRegion.cc b/src/db/db/dbDeepRegion.cc
index eb9f95fa9..46a1463ad 100644
--- a/src/db/db/dbDeepRegion.cc
+++ b/src/db/db/dbDeepRegion.cc
@@ -1364,7 +1364,7 @@ DeepRegion::run_check (db::edge_relation_type rel, bool different_polygons, cons
 
   std::auto_ptr<db::DeepEdgePairs> res (new db::DeepEdgePairs (polygons.derived ()));
 
-  db::CheckLocalOperation op (check, different_polygons, other_deep != 0, other->is_merged (), shielded);
+  db::CheckLocalOperation op (check, different_polygons, other_deep != 0, other && other->is_merged (), shielded);
 
   db::local_processor<db::PolygonRef, db::PolygonRef, db::EdgePair> proc (const_cast<db::Layout *> (&polygons.layout ()),
                                                                           const_cast<db::Cell *> (&polygons.initial_cell ()),