Index: bin/emerge
===================================================================
--- bin/emerge	(revision 7237)
+++ bin/emerge	(revision 7238)
@@ -1083,6 +1083,8 @@
 		self.pkg_node_map = {}
 		# Maps slot atom to digraph node for all nodes added to the graph.
 		self._slot_node_map = {}
+		# Maps nodes to the reasons they were selected for reinstallation.
+		self._reinstall_nodes = {}
 		self.mydbapi = {}
 		self._mydbapi_keys = ["SLOT", "DEPEND", "RDEPEND", "PDEPEND",
 			"USE", "IUSE", "PROVIDE", "RESTRICT"]
@@ -1204,18 +1206,23 @@
 
 	def _reinstall_for_flags(self, forced_flags,
 		orig_use, orig_iuse, cur_use, cur_iuse):
+		"""Return a set of flags that trigger reinstallation, or None if there
+		are no such flags."""
 		if "--newuse" in self.myopts:
-			if orig_iuse.symmetric_difference(
-				cur_iuse).difference(forced_flags):
-				return True
-			elif orig_iuse.intersection(orig_use) != \
-				cur_iuse.intersection(cur_use):
-				return True
+			flags = orig_iuse.symmetric_difference(
+				cur_iuse).difference(forced_flags)
+			if flags:
+				return flags
+			flags = orig_iuse.intersection(orig_use).symmetric_difference(
+				cur_iuse.intersection(cur_use))
+			if flags:
+				return flags
 		elif "changed-use" == self.myopts.get("--reinstall"):
-			if orig_iuse.intersection(orig_use) != \
-				cur_iuse.intersection(cur_use):
-				return True
-		return False
+			flags = orig_iuse.intersection(orig_use).symmetric_difference(
+				cur_iuse.intersection(cur_use))
+			if flags:
+				return flags
+		return None
 
 	def create(self, mybigkey, myparent=None, addme=1, myuse=None,
 		priority=DepPriority(), rev_dep=False, arg=None):
@@ -1286,6 +1293,7 @@
 					return 0
 				del e
 
+		reinstall_for_flags = None
 		merging=1
 		if mytype == "installed":
 			merging = 0
@@ -1299,6 +1307,7 @@
 			    If the package has new iuse flags or different use flags then if
 			    --newuse is specified, we need to merge the package. """
 			if merging == 0 and \
+				myroot == self.target_root and \
 				("--newuse" in self.myopts or
 				"--reinstall" in self.myopts) and \
 				vardbapi.cpv_exists(mykey):
@@ -1310,8 +1319,9 @@
 				iuses = set(filter_iuse_defaults(metadata["IUSE"].split()))
 				old_iuse = set(filter_iuse_defaults(
 					vardbapi.aux_get(mykey, ["IUSE"])[0].split()))
-				if self._reinstall_for_flags(
-					forced_flags, old_use, old_iuse, myuse, iuses):
+				reinstall_for_flags = self._reinstall_for_flags(
+					forced_flags, old_use, old_iuse, myuse, iuses)
+				if reinstall_for_flags:
 					merging = 1
 
 		if addme and merging == 1:
@@ -1379,6 +1389,8 @@
 				self._slot_node_map[myroot][slot_atom] = jbigkey
 				self.pkg_node_map[myroot][mykey] = jbigkey
 				self.useFlags[myroot][mykey] = myuse
+				if reinstall_for_flags:
+					self._reinstall_nodes[jbigkey] = reinstall_for_flags
 
 			if rev_dep and myparent:
 				self.digraph.addnode(myparent, jbigkey,
@@ -2874,7 +2886,8 @@
 					use_expand_hidden = \
 						pkgsettings["USE_EXPAND_HIDDEN"].lower().split()
 
-					def map_to_use_expand(myvals, forcedFlags=False):
+					def map_to_use_expand(myvals, forcedFlags=False,
+						removeHidden=True):
 						ret = {}
 						forced = {}
 						for exp in use_expand:
@@ -2889,13 +2902,32 @@
 						ret["USE"] = myvals
 						forced["USE"] = [val for val in myvals \
 							if val in forced_flags]
-						for exp in use_expand_hidden:
-							if exp in ret:
-								del ret[exp]
+						if removeHidden:
+							for exp in use_expand_hidden:
+								ret.pop(exp, None)
 						if forcedFlags:
 							return ret, forced
 						return ret
 
+					# Prevent USE_EXPAND_HIDDEN flags from being hidden if they
+					# are the only thing that triggered reinstallation.
+					reinst_flags_map = None
+					reinstall_for_flags = self._reinstall_nodes.get(pkg_node)
+					if reinstall_for_flags:
+						reinst_flags_map = map_to_use_expand(
+							list(reinstall_for_flags), removeHidden=False)
+						if reinst_flags_map["USE"]:
+							reinst_flags_map = None
+						else:
+							for k in reinst_flags_map.keys():
+								if not reinst_flags_map[k]:
+									del reinst_flags_map[k]
+					if reinst_flags_map and \
+						not set(reinst_flags_map).difference(
+						use_expand_hidden):
+						use_expand_hidden = set(use_expand_hidden).difference(
+							reinst_flags_map)
+
 					cur_iuse_map, iuse_forced = \
 						map_to_use_expand(cur_iuse, forcedFlags=True)
 					cur_use_map = map_to_use_expand(cur_use)