diff --git a/Source/OpenTK/Platform/Windows/WindowInfo.cs b/Source/OpenTK/Platform/Windows/WindowInfo.cs
index 21b800c8..b8ea7130 100644
--- a/Source/OpenTK/Platform/Windows/WindowInfo.cs
+++ b/Source/OpenTK/Platform/Windows/WindowInfo.cs
@@ -32,7 +32,7 @@ namespace OpenTK.Platform.Windows
         public override string ToString()
         {
             return String.Format("Windows.WindowInfo: Handle {0}{1}    Parent {2}",
-                this.Handle, System.Environment.NewLine, this.Parent.ToString());
+                this.Handle, System.Environment.NewLine, this.Parent != null ? this.Parent.ToString() : "null");
         }
 
     }
diff --git a/Source/OpenTK/Platform/X11/WindowInfo.cs b/Source/OpenTK/Platform/X11/WindowInfo.cs
index 39ae7b46..792d65ba 100644
--- a/Source/OpenTK/Platform/X11/WindowInfo.cs
+++ b/Source/OpenTK/Platform/X11/WindowInfo.cs
@@ -35,7 +35,7 @@ namespace OpenTK.Platform.X11
         public override string ToString()
         {
             return String.Format("X11.WindowInfo: Display {0}, Screen {1}, Handle {2}{3}    Parent {4}",
-                this.Display, this.Screen, this.Handle, System.Environment.NewLine, this.Parent.ToString());
+                this.Display, this.Screen, this.Handle, System.Environment.NewLine, this.Parent != null ? this.Parent.ToString() : "null");
         }
     }
 }