diff --git a/MatterControlLib/DesignTools/SupportGenerator.cs b/MatterControlLib/DesignTools/SupportGenerator.cs
index 7f9b2b16b..7d6506edc 100644
--- a/MatterControlLib/DesignTools/SupportGenerator.cs
+++ b/MatterControlLib/DesignTools/SupportGenerator.cs
@@ -308,7 +308,8 @@ namespace MatterHackers.MatterControl.DesignTools
 				if (fromBed)
 				{
 					i = GetNextBottom(i, kvp.Value);
-					if (kvp.Value[i].bottom)
+					if (i < kvp.Value.Count
+						&& kvp.Value[i].bottom)
 					{
 						AddSupportColumn(supportColumnsToAdd, xPos, yPos, 0, kvp.Value[i].z + .01);
 					}