diff --git a/OpenRA.Editor/Form1.cs b/OpenRA.Editor/Form1.cs
index 78df763411..cee9f96e0b 100644
--- a/OpenRA.Editor/Form1.cs
+++ b/OpenRA.Editor/Form1.cs
@@ -140,7 +140,16 @@ namespace OpenRA.Editor
 				if (DialogResult.OK != rd.ShowDialog())
 					return;
 
-				surface1.Bind(surface1.Map, surface1.TileSet, surface1.Palette);	// rebind it to invalidate all caches
+				surface1.Map.TopLeft = new int2((int)rd.cordonLeft.Value, (int)rd.cordonTop.Value);
+				surface1.Map.BottomRight = new int2((int)rd.cordonRight.Value, (int)rd.cordonBottom.Value);
+
+				if ((int)rd.width.Value != surface1.Map.MapSize.X || (int)rd.height.Value != surface1.Map.MapSize.Y)
+				{
+					surface1.Map.Resize((int)rd.width.Value, (int)rd.height.Value);
+					surface1.Bind(surface1.Map, surface1.TileSet, surface1.Palette);	// rebind it to invalidate all caches
+				}
+
+				surface1.Invalidate();
 			}
 		}
 	}
diff --git a/OpenRA.Editor/ResizeDialog.Designer.cs b/OpenRA.Editor/ResizeDialog.Designer.cs
index d712881805..3b39cc685c 100644
--- a/OpenRA.Editor/ResizeDialog.Designer.cs
+++ b/OpenRA.Editor/ResizeDialog.Designer.cs
@@ -196,6 +196,7 @@
 			this.Controls.Add(this.width);
 			this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedDialog;
 			this.Name = "ResizeDialog";
+			this.StartPosition = System.Windows.Forms.FormStartPosition.CenterParent;
 			this.Text = "Resize Map";
 			((System.ComponentModel.ISupportInitialize)(this.width)).EndInit();
 			((System.ComponentModel.ISupportInitialize)(this.cordonLeft)).EndInit();
diff --git a/OpenRA.Editor/Surface.cs b/OpenRA.Editor/Surface.cs
index 4ddbc13aa1..eee1abd48c 100644
--- a/OpenRA.Editor/Surface.cs
+++ b/OpenRA.Editor/Surface.cs
@@ -136,8 +136,8 @@ namespace OpenRA.Editor
 			if (Map == null) return;
 			if (TileSet == null) return;
 
-			for( var u = 0; u <= Map.BottomRight.X; u += ChunkSize )
-				for (var v = 0; v <= Map.BottomRight.Y; v += ChunkSize)
+			for( var u = 0; u < Map.MapSize.X; u += ChunkSize )
+				for (var v = 0; v < Map.MapSize.Y; v += ChunkSize)
 				{
 					var x = new int2(u/ChunkSize,v/ChunkSize);
 					if (!Chunks.ContainsKey(x)) Chunks[x] = RenderChunk(u / ChunkSize, v / ChunkSize);
diff --git a/OpenRA.FileFormats/Map/Map.cs b/OpenRA.FileFormats/Map/Map.cs
index 4ede89ce57..50a99810da 100644
--- a/OpenRA.FileFormats/Map/Map.cs
+++ b/OpenRA.FileFormats/Map/Map.cs
@@ -261,5 +261,22 @@ namespace OpenRA.FileFormats
 			foreach (var s in Smudges)
 				Console.WriteLine("\t{0} {1} {2}", s.Type, s.Location, s.Depth);
 		}
+
+		static T[,] ResizeArray<T>(T[,] ts, T t, int width, int height)
+		{
+			var result = new T[width, height];
+			for (var i = 0; i < width; i++)
+				for (var j = 0; j < height; j++)
+					result[i, j] = i <= ts.GetUpperBound(0) && j <= ts.GetUpperBound(1)
+						? ts[i, j] : t;
+			return result;
+		}
+
+		public void Resize(int width, int height)		// editor magic.
+		{
+			MapTiles = ResizeArray(MapTiles, MapTiles[0, 0], width, height);
+			MapResources = ResizeArray(MapResources, MapResources[0, 0], width, height);
+			MapSize = new int2(width, height);
+		}
 	}
 }