diff --git a/Source/Core/Editing/ClassicMode.cs b/Source/Core/Editing/ClassicMode.cs
index fc53e5c8..f36c4b28 100644
--- a/Source/Core/Editing/ClassicMode.cs
+++ b/Source/Core/Editing/ClassicMode.cs
@@ -84,6 +84,24 @@ namespace CodeImp.DoomBuilder.Editing
 
 		#region ================== Properties
 		
+		// Mouse status
+		public Vector2D MousePos { get { return mousepos; } }
+		public Vector2D MouseLastPos { get { return mouselastpos; } }
+		public Vector2D MouseMapPos { get { return mousemappos; } }
+		public Vector2D MouseDownPos { get { return mousedownpos; } }
+		public Vector2D MouseDownMapPos { get { return mousedownmappos; } }
+		public MouseButtons MouseButtons { get { return mousebuttons; } }
+		public bool IsMouseInside { get { return mouseinside; } }
+		public MouseButtons MouseDragging { get { return mousedragging; } }
+
+		// Selection
+		public bool IsSelecting { get { return selecting; } }
+		public Vector2D SelectionStart { get { return selectstart; } }
+		public RectangleF SelectionRect { get { return selectionrect; } }
+		
+		// Panning
+		public bool IsPanning { get { return panning; } }
+
 		#endregion
 
 		#region ================== Constructor / Disposer
diff --git a/Source/Core/Editing/EditMode.cs b/Source/Core/Editing/EditMode.cs
index 97e10275..0d508992 100644
--- a/Source/Core/Editing/EditMode.cs
+++ b/Source/Core/Editing/EditMode.cs
@@ -67,6 +67,9 @@ namespace CodeImp.DoomBuilder.Editing
 		// for checking the appropriate button on the toolbar.
 		public virtual string EditModeButtonName { get { return GetType().Name; } }
 
+		// Override this to provide a highlighted object, if applicable
+		public virtual object HighlightedObject { get { return null; } }
+
 		#endregion
 
 		#region ================== Constructor / Disposer
diff --git a/Source/Plugins/BuilderModes/ClassicModes/BrightnessMode.cs b/Source/Plugins/BuilderModes/ClassicModes/BrightnessMode.cs
index f6856aec..ab495997 100644
--- a/Source/Plugins/BuilderModes/ClassicModes/BrightnessMode.cs
+++ b/Source/Plugins/BuilderModes/ClassicModes/BrightnessMode.cs
@@ -83,6 +83,8 @@ namespace CodeImp.DoomBuilder.BuilderModes
 		
 		#region ================== Properties
 
+		public override object HighlightedObject { get { return highlighted; } }
+		
 		#endregion
 		
 		#region ================== Constructor / Disposer
diff --git a/Source/Plugins/BuilderModes/ClassicModes/EditSelectionMode.cs b/Source/Plugins/BuilderModes/ClassicModes/EditSelectionMode.cs
index e188fb6d..57955e24 100644
--- a/Source/Plugins/BuilderModes/ClassicModes/EditSelectionMode.cs
+++ b/Source/Plugins/BuilderModes/ClassicModes/EditSelectionMode.cs
@@ -138,6 +138,8 @@ namespace CodeImp.DoomBuilder.BuilderModes
 
 		#region ================== Properties
 
+		public override object HighlightedObject { get { return highlighted; } }
+		
 		// Just keep the base mode button checked
 		public override string EditModeButtonName { get { return General.Editing.PreviousStableMode.Name; } }
 
diff --git a/Source/Plugins/BuilderModes/ClassicModes/LinedefsMode.cs b/Source/Plugins/BuilderModes/ClassicModes/LinedefsMode.cs
index d59a3f48..df0211fc 100644
--- a/Source/Plugins/BuilderModes/ClassicModes/LinedefsMode.cs
+++ b/Source/Plugins/BuilderModes/ClassicModes/LinedefsMode.cs
@@ -67,6 +67,8 @@ namespace CodeImp.DoomBuilder.BuilderModes
 
 		#region ================== Properties
 
+		public override object HighlightedObject { get { return highlighted; } }
+		
 		#endregion
 
 		#region ================== Constructor / Disposer
diff --git a/Source/Plugins/BuilderModes/ClassicModes/SectorsMode.cs b/Source/Plugins/BuilderModes/ClassicModes/SectorsMode.cs
index 973170e7..5bef100e 100644
--- a/Source/Plugins/BuilderModes/ClassicModes/SectorsMode.cs
+++ b/Source/Plugins/BuilderModes/ClassicModes/SectorsMode.cs
@@ -68,6 +68,8 @@ namespace CodeImp.DoomBuilder.BuilderModes
 
 		#region ================== Properties
 
+		public override object HighlightedObject { get { return highlighted; } }
+
 		#endregion
 
 		#region ================== Constructor / Disposer
@@ -853,16 +855,13 @@ namespace CodeImp.DoomBuilder.BuilderModes
 		public void MakeDoor()
 		{
 			// Highlighted item not selected?
-			if(!highlighted.Selected)
+			if((highlighted != null) && !highlighted.Selected)
 			{
-				if(highlighted != null)
-				{
-					// Make this the only selection
-					General.Map.Map.ClearSelectedSectors();
-					General.Map.Map.ClearSelectedLinedefs();
-					SelectSector(highlighted, true, false);
-					General.Interface.RedrawDisplay();
-				}
+				// Make this the only selection
+				General.Map.Map.ClearSelectedSectors();
+				General.Map.Map.ClearSelectedLinedefs();
+				SelectSector(highlighted, true, false);
+				General.Interface.RedrawDisplay();
 			}
 			
 			// Anything selected?
diff --git a/Source/Plugins/BuilderModes/ClassicModes/ThingsMode.cs b/Source/Plugins/BuilderModes/ClassicModes/ThingsMode.cs
index f3bbf801..813d113d 100644
--- a/Source/Plugins/BuilderModes/ClassicModes/ThingsMode.cs
+++ b/Source/Plugins/BuilderModes/ClassicModes/ThingsMode.cs
@@ -68,6 +68,8 @@ namespace CodeImp.DoomBuilder.BuilderModes
 
 		#region ================== Properties
 
+		public override object HighlightedObject { get { return highlighted; } }
+
 		#endregion
 
 		#region ================== Constructor / Disposer
diff --git a/Source/Plugins/BuilderModes/ClassicModes/VerticesMode.cs b/Source/Plugins/BuilderModes/ClassicModes/VerticesMode.cs
index f03b4eef..e385230f 100644
--- a/Source/Plugins/BuilderModes/ClassicModes/VerticesMode.cs
+++ b/Source/Plugins/BuilderModes/ClassicModes/VerticesMode.cs
@@ -64,6 +64,8 @@ namespace CodeImp.DoomBuilder.BuilderModes
 
 		#region ================== Properties
 
+		public override object HighlightedObject { get { return highlighted; } }
+
 		#endregion
 
 		#region ================== Constructor / Disposer
diff --git a/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs b/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs
index e65334ee..65df0a20 100644
--- a/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs
+++ b/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs
@@ -88,6 +88,35 @@ namespace CodeImp.DoomBuilder.BuilderModes
 		
 		#region ================== Properties
 
+		public override object HighlightedObject
+		{
+			get
+			{
+				// Geometry picked?
+				if(target.picked is VisualGeometry)
+				{
+					VisualGeometry pickedgeo = (target.picked as VisualGeometry);
+
+					if(pickedgeo.Sidedef != null)
+						return pickedgeo.Sidedef;
+					else if(pickedgeo.Sector != null)
+						return pickedgeo.Sector;
+					else
+						return null;
+				}
+				// Thing picked?
+				else if(target.picked is VisualThing)
+				{
+					VisualThing pickedthing = (target.picked as VisualThing);
+					return pickedthing.Thing;
+				}
+				else
+				{
+					return null;
+				}
+			}
+		}
+
 		public IRenderer3D Renderer { get { return renderer; } }
 		
 		public bool IsSingleSelection { get { return singleselection; } }
diff --git a/Tests/ErrorChecking/sectornotclosed_a.dbs b/Tests/ErrorChecking/sectornotclosed_a.dbs
new file mode 100644
index 00000000..78f0df99
--- /dev/null
+++ b/Tests/ErrorChecking/sectornotclosed_a.dbs
@@ -0,0 +1,30 @@
+type = "Doom Builder Map Settings Configuration";
+gameconfig = "ZDoom_Doom.cfg";
+strictpatches = 0;
+
+maps
+{
+	
+	MAP01
+	{
+		
+		resources
+		{
+		}
+		
+		
+		grid
+		{
+			background = "";
+			backsource = 0;
+			backoffsetx = 0;
+			backoffsety = 0;
+			backscalex = 100;
+			backscaley = 100;
+			gridsize = 32;
+		}
+		
+	}
+	
+}
+
diff --git a/Tests/ErrorChecking/sectornotclosed_a.wad b/Tests/ErrorChecking/sectornotclosed_a.wad
new file mode 100644
index 00000000..f3ae9923
Binary files /dev/null and b/Tests/ErrorChecking/sectornotclosed_a.wad differ