Index: pym/portage.py
===================================================================
--- pym/portage.py	(revision 4018)
+++ pym/portage.py	(revision 4019)
@@ -318,6 +318,10 @@
 		self.okeys=[]
 
 	def addnode(self,mykey,myparent):
+		if mykey == myparent:
+			# Refuse to make a node depend on itself so that the caller doesn't
+			# accidentally create a bogus circular dependency.
+			myparent = None
 		if not self.dict.has_key(mykey):
 			self.okeys.append(mykey)
 			if myparent is None:
Index: bin/emerge
===================================================================
--- bin/emerge	(revision 4018)
+++ bin/emerge	(revision 4019)
@@ -689,10 +689,14 @@
 		#"no downgrade" emerge
 		"""
 
-		jbigkey=string.join(mybigkey)
-		# Prevent cycles where packages are already in the digraph
-		if self.digraph.hasnode(jbigkey+" merge") or self.digraph.hasnode(jbigkey+" nomerge"):
+		jbigkey = " ".join(mybigkey) + " merge"
+		if self.digraph.hasnode(jbigkey):
+			if addme:
+				self.digraph.addnode(jbigkey, myparent)
 			return 1
+		jbigkey = " ".join(mybigkey) + " nomerge"
+		if self.digraph.hasnode(jbigkey):
+			return 1
 		
 		self.spinner.update()
 		mytype,myroot,mykey=mybigkey