diff --git a/Part 4 - Concurrency/3. Sequences of coincidence.md b/Part 4 - Concurrency/3. Sequences of coincidence.md
index 76f664e..bf4df8f 100644
--- a/Part 4 - Concurrency/3. Sequences of coincidence.md	
+++ b/Part 4 - Concurrency/3. Sequences of coincidence.md	
@@ -117,7 +117,7 @@ source.Window(3)
     {
         var id = windowIdx++;
         Console.WriteLine("--Starting new window");
-        var windowName = "Window" + thisWindowIdx;
+        var windowName = "Window" + windowIdx;
         window.Subscribe(
             value => Console.WriteLine("{0} : {1}", windowName, value),
             ex => Console.WriteLine("{0} : {1}", windowName, ex),