diff --git a/Naive Bayes Classifier/NaiveBayes.playground/Contents.swift b/Naive Bayes Classifier/NaiveBayes.playground/Contents.swift
index 66aefaa32..6a2e01aab 100644
--- a/Naive Bayes Classifier/NaiveBayes.playground/Contents.swift	
+++ b/Naive Bayes Classifier/NaiveBayes.playground/Contents.swift	
@@ -1,5 +1,10 @@
 import Foundation
 
+// last checked with Xcode 9.0b4
+#if swift(>=4.0)
+print("Hello, Swift 4!")
+#endif
+
 /*:
  ## Naive Bayes Classifier