diff --git a/Rx.playground/Pages/Mathematical_and_Aggregate_Operators.xcplaygroundpage/Contents.swift b/Rx.playground/Pages/Mathematical_and_Aggregate_Operators.xcplaygroundpage/Contents.swift
index e3f8598f..398abac4 100644
--- a/Rx.playground/Pages/Mathematical_and_Aggregate_Operators.xcplaygroundpage/Contents.swift
+++ b/Rx.playground/Pages/Mathematical_and_Aggregate_Operators.xcplaygroundpage/Contents.swift
@@ -61,6 +61,7 @@ example("concat") {
     
     variable.value = subject2
     
+    subject2.onNext("I would be ignored")
     subject2.onNext("🐱")
     
     subject1.onCompleted()