Index: pym/portage/__init__.py
===================================================================
--- pym/portage/__init__.py	(revision 12669)
+++ pym/portage/__init__.py	(working copy)
@@ -2079,9 +2079,9 @@
 
 		# Escape anything except ".*" which is supposed
 		# to pass through from _get_implicit_iuse()
-		regex = sorted(re.escape(x) for x in iuse_implicit)
-		regex = "^(%s)$" % "|".join(regex)
-		regex = regex.replace("\\.\\*", ".*")
+		regex = re.escape('|'.join(sorted(iuse_implicit)))
+		regex = regex.replace('\\|', '|').replace('\\.\\*', '.*')
+		regex = '^(%s)$' % regex
 		self.configdict["pkg"]["PORTAGE_IUSE"] = regex
 
 		ebuild_force_test = self.get("EBUILD_FORCE_TEST") == "1"