diff --git a/Source/GLControl/CarbonGLControl.cs b/Source/GLControl/CarbonGLControl.cs
index 380a735f..58589f95 100644
--- a/Source/GLControl/CarbonGLControl.cs
+++ b/Source/GLControl/CarbonGLControl.cs
@@ -54,10 +54,13 @@ namespace OpenTK
 		}
 
 		private int GetYOffset(){
-			System.Drawing.Point offset = control.PointToScreen(control.Location);
-			System.Drawing.Point windowOffset = control.TopLevelControl.PointToScreen(System.Drawing.Point.Empty);
-			int relativeY = offset.Y-windowOffset.Y; //control.TopLevelControl.Location.Y is not the same as windowOffset.Y for some reason.
-			return control.TopLevelControl.ClientSize.Height - control.Bottom - relativeY;
+			if (control.TopLevelControl != null) {
+				System.Drawing.Point offset = control.PointToScreen (control.Location);
+				System.Drawing.Point windowOffset = control.TopLevelControl.PointToScreen (System.Drawing.Point.Empty);
+				int relativeY = offset.Y - windowOffset.Y; //control.TopLevelControl.Location.Y is not the same as windowOffset.Y for some reason.
+				return control.TopLevelControl.ClientSize.Height - control.Bottom - relativeY;
+			}
+			return control.Location.Y;
 		}
 
         #region IGLControl Members