diff --git a/MatterControlLib/DesignTools/SupportGenerator.cs b/MatterControlLib/DesignTools/SupportGenerator.cs
index f19e7338f..c38f2926a 100644
--- a/MatterControlLib/DesignTools/SupportGenerator.cs
+++ b/MatterControlLib/DesignTools/SupportGenerator.cs
@@ -80,8 +80,8 @@ namespace MatterHackers.MatterControl.DesignTools
 
 	public class SupportGenerator
 	{
-		private double minimumSupportHeight;
-		private InteractiveScene scene;
+		private readonly double minimumSupportHeight;
+		private readonly InteractiveScene scene;
 
 		public SupportGenerator(InteractiveScene scene, double minimumSupportHeight)
 		{
@@ -427,14 +427,15 @@ namespace MatterHackers.MatterControl.DesignTools
 				{
 					// add a single plane at the bed so we always know the bed is a top
 					detectedPlanes.Add((x, y), new List<(double z, bool bottom)>());
-					detectedPlanes[(x, y)].Add((0, false));
 
 					IntersectInfo upHit = null;
-
 					for (double yOffset = -1; yOffset <= 1; yOffset++)
 					{
 						for (double xOffset = -1; xOffset <= 1; xOffset++)
 						{
+							var singlXyPlanes = new List<(double z, bool bottom)>();
+							singlXyPlanes.Add((0, false));
+
 							var halfPillar = PillarSize / 2;
 							var yPos = (gridBounds.Bottom + y) * PillarSize + halfPillar + (yOffset * halfPillar);
 							var xPos = (gridBounds.Left + x) * PillarSize + halfPillar + (xOffset * halfPillar);
@@ -446,7 +447,7 @@ namespace MatterHackers.MatterControl.DesignTools
 								upHit = traceData.GetClosestIntersection(upRay);
 								if (upHit != null)
 								{
-									detectedPlanes[(x, y)].Add((upHit.HitPosition.Z, true));
+									singlXyPlanes.Add((upHit.HitPosition.Z, true));
 
 									// make a new ray just past the last hit to keep looking for up hits
 									upRay = new Ray(new Vector3(xPos, yPos, upHit.HitPosition.Z + .001), Vector3.UnitZ, intersectionType: IntersectionType.FrontFace);
@@ -460,12 +461,14 @@ namespace MatterHackers.MatterControl.DesignTools
 								upHit = traceData.GetClosestIntersection(upRay);
 								if (upHit != null)
 								{
-									detectedPlanes[(x, y)].Add((upHit.HitPosition.Z, false));
+									singlXyPlanes.Add((upHit.HitPosition.Z, false));
 
 									// make a new ray just past the last hit to keep looking for up hits
 									upRay = new Ray(new Vector3(xPos, yPos, upHit.HitPosition.Z + .001), Vector3.UnitZ, intersectionType: IntersectionType.BackFace);
 								}
 							} while (upHit != null);
+
+							// union the sigleXyPlanes into detectedPlanes[(x, y)]
 						}
 					}
 				}
diff --git a/Tests/MatterControl.Tests/MatterControl/SupportGeneratorTests.cs b/Tests/MatterControl.Tests/MatterControl/SupportGeneratorTests.cs
index 458404354..599c4256f 100644
--- a/Tests/MatterControl.Tests/MatterControl/SupportGeneratorTests.cs
+++ b/Tests/MatterControl.Tests/MatterControl/SupportGeneratorTests.cs
@@ -36,6 +36,8 @@ using MatterHackers.Agg.Platform;
 using MatterHackers.DataConverters3D;
 using MatterHackers.MatterControl.DesignTools;
 using MatterHackers.MatterControl.Tests.Automation;
+using MatterHackers.PolygonMesh;
+using MatterHackers.PolygonMesh.Processors;
 using MatterHackers.VectorMath;
 using NUnit.Framework;
 
@@ -468,6 +470,28 @@ namespace MatterControl.Tests.MatterControl
 
 				Assert.AreEqual(bedSupportCount, airSupportCount, "Same number of support columns in each space.");
 			}
+
+			// load a complex part that should have no support required
+			{
+				InteractiveScene scene = new InteractiveScene();
+
+				var meshPath = TestContext.CurrentContext.ResolveProjectPath(4, "Tests", "TestData", "TestParts", "NoSupportNeeded.stl");
+
+				var supportObject = new Object3D()
+				{
+					Mesh = StlProcessing.Load(meshPath, CancellationToken.None)
+				};
+
+				var aabbCube = supportObject.GetAxisAlignedBoundingBox();
+				// move it so the bottom is on the bed
+				supportObject.Matrix = Matrix4X4.CreateTranslation(0, 0, -aabbCube.MinXYZ.Z);
+				scene.Children.Add(supportObject);
+
+				var supportGenerator = new SupportGenerator(scene, minimumSupportHeight);
+				supportGenerator.SupportType = SupportGenerator.SupportGenerationType.Normal;
+				await supportGenerator.Create(null, CancellationToken.None);
+				Assert.AreEqual(1, scene.Children.Count, "We should not have added support");
+			}
 		}
 
 		[Test, Category("Support Generator")]
diff --git a/Tests/TestData/TestParts/NoSupportNeeded.stl b/Tests/TestData/TestParts/NoSupportNeeded.stl
new file mode 100644
index 000000000..7099d570c
Binary files /dev/null and b/Tests/TestData/TestParts/NoSupportNeeded.stl differ