Index: pym/portage/dep.py
===================================================================
--- pym/portage/dep.py	(revision 14242)
+++ pym/portage/dep.py	(working copy)
@@ -1007,6 +1007,17 @@
 	cp = getattr(mydep, "cp", None)
 	if cp is not None:
 		return cp
+
+	# Why does this patch cause `emerge -puD world`
+	# to reinstall packages unecessarily?
+	try:
+		return Atom(mydep).cp
+	except InvalidAtom:
+		try:
+			return Atom('=' + mydep).cp
+		except InvalidAtom:
+			pass
+
 	mydep = dep_getcpv(mydep)
 	if mydep and isspecific(mydep):
 		mysplit = catpkgsplit(mydep)