Index: pym/portage/dbapi/vartree.py
===================================================================
--- pym/portage/dbapi/vartree.py	(revision 13920)
+++ pym/portage/dbapi/vartree.py	(working copy)
@@ -1425,7 +1425,7 @@
 			h = self._new_hash()
 			# Always use a constant utf_8 encoding here, since
 			# the "default" encoding can change.
-			h.update(s)
+			h.update(s.encode('utf_8', 'replace'))
 			h = h.hexdigest()
 			h = h[-self._hex_chars:]
 			h = int(h, 16)