diff --git a/ch13/chapter13.playground/Sources/MetalView.swift b/ch13/chapter13.playground/Sources/MetalView.swift
index 37c8100..7120f0b 100755
--- a/ch13/chapter13.playground/Sources/MetalView.swift
+++ b/ch13/chapter13.playground/Sources/MetalView.swift
@@ -27,7 +27,6 @@ public class MetalView: MTKView, NSWindowDelegate {
     }
     
     override public func drawRect(dirtyRect: NSRect) {
-        super.drawRect(dirtyRect)
         if let drawable = currentDrawable {
             let commandBuffer = queue.commandBuffer()
             let commandEncoder = commandBuffer.computeCommandEncoder()