--- a/compiler/PPCDelegateNode.st	Fri Jul 24 15:06:54 2015 +0100
+++ b/compiler/PPCDelegateNode.st	Mon Aug 17 12:13:16 2015 +0100
@@ -17,6 +17,7 @@
 !
 
 child: whatever
+    self assert: (whatever == self) not.
     child := whatever 
 !
 
@@ -45,6 +46,7 @@
 !PPCDelegateNode methodsFor:'transformation'!
 
 replace: node with: anotherNode
+    self assert: (anotherNode == self) not.
     child == node ifTrue: [ child := anotherNode ]
 ! !