diff -r 0347e9bc883e -r 5d2c9d36da9d src/primitives.cpp
--- a/src/primitives.cpp	Sat Mar 03 16:59:03 2018 +0200
+++ b/src/primitives.cpp	Sat Mar 03 17:25:12 2018 +0200
@@ -316,12 +316,13 @@
 				Vertex v1 = {x1, y1, z1};
 				Vertex v2 = {x2, y2, z2};
 				Vertex v3 = {x3, y3, z3};
+
+				if (type == Cylinder)
+					qSwap(v1, v3);
+
 				LDQuadrilateral* quad = model.emplace<LDQuadrilateral>(v0, v1, v2, v3);
 				quad->setColor(MainColor);
 
-				if (type == Cylinder)
-					quad->invert();
-
 				if (type == Cylinder or type == Cone)
 					conditionalLineSegments.append(i);
 			}