diff --git a/Demo/threads/fcmp.py b/Demo/threads/fcmp.py
index 37a2087ebee..83ebe011035 100644
--- a/Demo/threads/fcmp.py
+++ b/Demo/threads/fcmp.py
@@ -9,7 +9,7 @@ def fringe( co, list ):
         if type(x) is type([]):
             fringe(co, x)
         else:
-            co.detach(x)
+            co.back(x)
 
 def printinorder( list ):
     co = Coroutine()