diff --git a/Threaded Binary Tree/ThreadedBinaryTree.playground/Contents.swift b/Threaded Binary Tree/ThreadedBinaryTree.playground/Contents.swift
index 4ce9d8157..ece1966e0 100644
--- a/Threaded Binary Tree/ThreadedBinaryTree.playground/Contents.swift	
+++ b/Threaded Binary Tree/ThreadedBinaryTree.playground/Contents.swift	
@@ -1,10 +1,5 @@
 //: Playground - noun: a place where people can play
 
-// last checked with Xcode 9.0b4
-#if swift(>=4.0)
-print("Hello, Swift 4!")
-#endif
-
 // Simple little debug function to make testing output pretty
 func check(_ tree: ThreadedBinaryTree<Int>?) {
   if let tree = tree {
diff --git a/Threaded Binary Tree/ThreadedBinaryTree.playground/playground.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist b/Threaded Binary Tree/ThreadedBinaryTree.playground/playground.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist
new file mode 100644
index 000000000..18d981003
--- /dev/null
+++ b/Threaded Binary Tree/ThreadedBinaryTree.playground/playground.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist	
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>