diff --git a/floorplan/3D/WallsViaCuttedQuads.h b/floorplan/3D/WallsViaCuttedQuads.h
index a8e119d..4157366 100644
--- a/floorplan/3D/WallsViaCuttedQuads.h
+++ b/floorplan/3D/WallsViaCuttedQuads.h
@@ -265,8 +265,13 @@ namespace Floorplan3D {
 
 			for (const Floorplan::FloorObstacleWallDoor* door : doors) {
 
-				const Point2 pds = door->getStart(wall.line);
-				const Point2 pde = door->getEnd(wall.line);
+				Point2 pds = door->getStart(wall.line);
+				Point2 pde = door->getEnd(wall.line);
+
+				// inverted door, swap start and end for correct triangle order
+				if (door->leftRight) {
+					std::swap(pds, pde);
+				}
 
 				const Point3  dp1(pds.x, pds.y, z1);
 				const Point3  dp2(pde.x, pde.y, z1);