diff --git a/Source/Core/Map/MapSet.cs b/Source/Core/Map/MapSet.cs
index 9cb23d7..3227400 100644
--- a/Source/Core/Map/MapSet.cs
+++ b/Source/Core/Map/MapSet.cs
@@ -2946,9 +2946,18 @@ namespace CodeImp.DoomBuilder.Map
 			BlockMap<BlockEntry> blockmap = new BlockMap<BlockEntry>(area);
 			blockmap.AddVerticesSet(verts);
 			blockmap.AddLinedefsSet(lines);
+			int bmWidth = blockmap.Size.Width;
+			int bmHeight = blockmap.Size.Height;
+			BlockEntry[,] bmap = blockmap.Map;
 
 			HashSet<Vertex> splitverts = new HashSet<Vertex>();
 			HashSet<Sector> changedsectors = (mergemode == MergeGeometryMode.REPLACE ? General.Map.Map.GetSectorsFromLinedefs(changedlines) : new HashSet<Sector>());
+			HashSet<Vertex> lineverts = new HashSet<Vertex>();
+			foreach (Linedef l in lines)
+			{
+				lineverts.Add(l.Start);
+				lineverts.Add(l.End);
+			}
 
 			foreach (Vertex v in verts)
 			{
@@ -2990,6 +2999,7 @@ namespace CodeImp.DoomBuilder.Map
 								Linedef nl = l.Split(v);
 								if (nl == null) return false;
 								v.Marked = true; //mxd
+								splitverts.Add(v); //mxd
 
 								// Add the new line to the list
 								lines.Add(nl);