--- a/tests/test-i18n.t	Thu Oct 12 22:09:11 2017 +0900
+++ b/tests/test-i18n.t	Fri Oct 13 21:36:10 2017 +0900
@@ -48,3 +48,23 @@
   $ $PYTHON check-translation.py *.po
   $ $PYTHON check-translation.py --doctest
   $ cd $TESTTMP
+
+Check i18n cache isn't reused after encoding change:
+
+  $ cat > $TESTTMP/encodingchange.py << EOF
+  > from mercurial import encoding, registrar
+  > from mercurial.i18n import _
+  > cmdtable = {}
+  > command = registrar.command(cmdtable)
+  > @command(b'encodingchange', norepo=True)
+  > def encodingchange(ui):
+  >     for encode in (b'ascii', b'UTF-8', b'ascii', b'UTF-8'):
+  >         encoding.encoding = encode
+  >         ui.write(b'%s\n' % _(b'(EXPERIMENTAL)'))
+  > EOF
+
+  $ LANGUAGE=ja hg --config extensions.encodingchange=$TESTTMP/encodingchange.py encodingchange
+  (?????)
+  (\xe5\xae\x9f\xe9\xa8\x93\xe7\x9a\x84\xe5\xae\x9f\xe8\xa3\x85) (esc)
+  (?????)
+  (\xe5\xae\x9f\xe9\xa8\x93\xe7\x9a\x84\xe5\xae\x9f\xe8\xa3\x85) (esc)