diff --git a/Source/Plugins/BuilderModes/ClassicModes/DragGeometryMode.cs b/Source/Plugins/BuilderModes/ClassicModes/DragGeometryMode.cs
index 4077d0a4430ec8ab95a9ffb715d90f06ffad9e29..c7579b27a982add3d80b2ad4c091cc961dca8061 100755
--- a/Source/Plugins/BuilderModes/ClassicModes/DragGeometryMode.cs
+++ b/Source/Plugins/BuilderModes/ClassicModes/DragGeometryMode.cs
@@ -454,6 +454,9 @@ namespace CodeImp.DoomBuilder.BuilderModes
 						if (ld.Args[0] == 0) // First argument of the action is the sector tag. 0 is not a valid value
 							continue;
 
+						if (ld.Front == null) // Must have a front side
+							continue;
+
 						controlsectors.Add(ld.Front.Sector);
 
 						foreach (Sector s in draggedsectors)