diff --git a/aclocal.m4 b/aclocal.m4
index fdba321..c6a40fe 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -20,18 +20,18 @@ You have another version of autoconf.  It may work, but is not guaranteed to.
 If you have problems, you may need to regenerate the build system entirely.
 To do so, use the procedure documented by the package, typically 'autoreconf'.])])
 
-# intlmacosx.m4 serial 5 (gettext-0.18.2)
-dnl Copyright (C) 2004-2014, 2016 Free Software Foundation, Inc.
+# intlmacosx.m4 serial 8 (gettext-0.20.2)
+dnl Copyright (C) 2004-2014, 2016, 2019-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 dnl
 dnl This file can be used in projects which are not available under
-dnl the GNU General Public License or the GNU Library General Public
+dnl the GNU General Public License or the GNU Lesser General Public
 dnl License but which still want to provide support for the GNU gettext
 dnl functionality.
 dnl Please note that the actual code of the GNU gettext library is covered
-dnl by the GNU Library General Public License, and the rest of the GNU
+dnl by the GNU Lesser General Public License, and the rest of the GNU
 dnl gettext package is covered by the GNU General Public License.
 dnl They are *not* in the public domain.
 
@@ -39,7 +39,7 @@ dnl Checks for special options needed on Mac OS X.
 dnl Defines INTL_MACOSX_LIBS.
 AC_DEFUN([gt_INTL_MACOSX],
 [
-  dnl Check for API introduced in Mac OS X 10.2.
+  dnl Check for API introduced in Mac OS X 10.4.
   AC_CACHE_CHECK([for CFPreferencesCopyAppValue],
     [gt_cv_func_CFPreferencesCopyAppValue],
     [gt_save_LIBS="$LIBS"
@@ -55,23 +55,32 @@ AC_DEFUN([gt_INTL_MACOSX],
     AC_DEFINE([HAVE_CFPREFERENCESCOPYAPPVALUE], [1],
       [Define to 1 if you have the Mac OS X function CFPreferencesCopyAppValue in the CoreFoundation framework.])
   fi
-  dnl Check for API introduced in Mac OS X 10.3.
-  AC_CACHE_CHECK([for CFLocaleCopyCurrent], [gt_cv_func_CFLocaleCopyCurrent],
+  dnl Don't check for the API introduced in Mac OS X 10.5, CFLocaleCopyCurrent,
+  dnl because in macOS 10.13.4 it has the following behaviour:
+  dnl When two or more languages are specified in the
+  dnl "System Preferences > Language & Region > Preferred Languages" panel,
+  dnl it returns en_CC where CC is the territory (even when English is not among
+  dnl the preferred languages!).  What we want instead is what
+  dnl CFLocaleCopyCurrent returned in earlier macOS releases and what
+  dnl CFPreferencesCopyAppValue still returns, namely ll_CC where ll is the
+  dnl first among the preferred languages and CC is the territory.
+  AC_CACHE_CHECK([for CFLocaleCopyPreferredLanguages], [gt_cv_func_CFLocaleCopyPreferredLanguages],
     [gt_save_LIBS="$LIBS"
      LIBS="$LIBS -Wl,-framework -Wl,CoreFoundation"
      AC_LINK_IFELSE(
        [AC_LANG_PROGRAM(
           [[#include <CoreFoundation/CFLocale.h>]],
-          [[CFLocaleCopyCurrent();]])],
-       [gt_cv_func_CFLocaleCopyCurrent=yes],
-       [gt_cv_func_CFLocaleCopyCurrent=no])
+          [[CFLocaleCopyPreferredLanguages();]])],
+       [gt_cv_func_CFLocaleCopyPreferredLanguages=yes],
+       [gt_cv_func_CFLocaleCopyPreferredLanguages=no])
      LIBS="$gt_save_LIBS"])
-  if test $gt_cv_func_CFLocaleCopyCurrent = yes; then
-    AC_DEFINE([HAVE_CFLOCALECOPYCURRENT], [1],
-      [Define to 1 if you have the Mac OS X function CFLocaleCopyCurrent in the CoreFoundation framework.])
+  if test $gt_cv_func_CFLocaleCopyPreferredLanguages = yes; then
+    AC_DEFINE([HAVE_CFLOCALECOPYPREFERREDLANGUAGES], [1],
+      [Define to 1 if you have the Mac OS X function CFLocaleCopyPreferredLanguages in the CoreFoundation framework.])
   fi
   INTL_MACOSX_LIBS=
-  if test $gt_cv_func_CFPreferencesCopyAppValue = yes || test $gt_cv_func_CFLocaleCopyCurrent = yes; then
+  if test $gt_cv_func_CFPreferencesCopyAppValue = yes \
+     || test $gt_cv_func_CFLocaleCopyPreferredLanguages = yes; then
     INTL_MACOSX_LIBS="-Wl,-framework -Wl,CoreFoundation"
   fi
   AC_SUBST([INTL_MACOSX_LIBS])
diff --git a/configure b/configure
index a9b0bda..5bca799 100755
--- a/configure
+++ b/configure
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.69 for tinmop 0.4.1.
+# Generated by GNU Autoconf 2.69 for tinmop 0.4.2.
 #
 # Report bugs to <https://notabug.org/cage/tinmop/>.
 #
@@ -580,8 +580,8 @@ MAKEFLAGS=
 # Identity of this package.
 PACKAGE_NAME='tinmop'
 PACKAGE_TARNAME='tinmop'
-PACKAGE_VERSION='0.4.1'
-PACKAGE_STRING='tinmop 0.4.1'
+PACKAGE_VERSION='0.4.2'
+PACKAGE_STRING='tinmop 0.4.2'
 PACKAGE_BUGREPORT='https://notabug.org/cage/tinmop/'
 PACKAGE_URL=''
 
@@ -1279,7 +1279,7 @@ if test "$ac_init_help" = "long"; then
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-\`configure' configures tinmop 0.4.1 to adapt to many kinds of systems.
+\`configure' configures tinmop 0.4.2 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1350,7 +1350,7 @@ fi
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of tinmop 0.4.1:";;
+     short | recursive ) echo "Configuration of tinmop 0.4.2:";;
    esac
   cat <<\_ACEOF
 
@@ -1452,7 +1452,7 @@ fi
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-tinmop configure 0.4.1
+tinmop configure 0.4.2
 generated by GNU Autoconf 2.69
 
 Copyright (C) 2012 Free Software Foundation, Inc.
@@ -1632,7 +1632,7 @@ cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by tinmop $as_me 0.4.1, which was
+It was created by tinmop $as_me 0.4.2, which was
 generated by GNU Autoconf 2.69.  Invocation command line was
 
   $ $0 $@
@@ -2497,7 +2497,7 @@ fi
 
 # Define the identity of the package.
  PACKAGE='tinmop'
- VERSION='0.4.1'
+ VERSION='0.4.2'
 
 
 cat >>confdefs.h <<_ACEOF
@@ -5092,9 +5092,9 @@ $as_echo "$gt_cv_func_CFPreferencesCopyAppValue" >&6; }
 $as_echo "#define HAVE_CFPREFERENCESCOPYAPPVALUE 1" >>confdefs.h
 
   fi
-    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for CFLocaleCopyCurrent" >&5
-$as_echo_n "checking for CFLocaleCopyCurrent... " >&6; }
-if ${gt_cv_func_CFLocaleCopyCurrent+:} false; then :
+                    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for CFLocaleCopyPreferredLanguages" >&5
+$as_echo_n "checking for CFLocaleCopyPreferredLanguages... " >&6; }
+if ${gt_cv_func_CFLocaleCopyPreferredLanguages+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   gt_save_LIBS="$LIBS"
@@ -5105,29 +5105,30 @@ else
 int
 main ()
 {
-CFLocaleCopyCurrent();
+CFLocaleCopyPreferredLanguages();
   ;
   return 0;
 }
 _ACEOF
 if ac_fn_c_try_link "$LINENO"; then :
-  gt_cv_func_CFLocaleCopyCurrent=yes
+  gt_cv_func_CFLocaleCopyPreferredLanguages=yes
 else
-  gt_cv_func_CFLocaleCopyCurrent=no
+  gt_cv_func_CFLocaleCopyPreferredLanguages=no
 fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext conftest.$ac_ext
      LIBS="$gt_save_LIBS"
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gt_cv_func_CFLocaleCopyCurrent" >&5
-$as_echo "$gt_cv_func_CFLocaleCopyCurrent" >&6; }
-  if test $gt_cv_func_CFLocaleCopyCurrent = yes; then
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gt_cv_func_CFLocaleCopyPreferredLanguages" >&5
+$as_echo "$gt_cv_func_CFLocaleCopyPreferredLanguages" >&6; }
+  if test $gt_cv_func_CFLocaleCopyPreferredLanguages = yes; then
 
-$as_echo "#define HAVE_CFLOCALECOPYCURRENT 1" >>confdefs.h
+$as_echo "#define HAVE_CFLOCALECOPYPREFERREDLANGUAGES 1" >>confdefs.h
 
   fi
   INTL_MACOSX_LIBS=
-  if test $gt_cv_func_CFPreferencesCopyAppValue = yes || test $gt_cv_func_CFLocaleCopyCurrent = yes; then
+  if test $gt_cv_func_CFPreferencesCopyAppValue = yes \
+     || test $gt_cv_func_CFLocaleCopyPreferredLanguages = yes; then
     INTL_MACOSX_LIBS="-Wl,-framework -Wl,CoreFoundation"
   fi
 
@@ -7141,7 +7142,7 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
 # report actual input values of CONFIG_FILES etc. instead of their
 # values after options handling.
 ac_log="
-This file was extended by tinmop $as_me 0.4.1, which was
+This file was extended by tinmop $as_me 0.4.2, which was
 generated by GNU Autoconf 2.69.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -7198,7 +7199,7 @@ _ACEOF
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`"
 ac_cs_version="\\
-tinmop config.status 0.4.1
+tinmop config.status 0.4.2
 configured by $0, generated by GNU Autoconf 2.69,
   with options \\"\$ac_cs_config\\"
 
diff --git a/configure.ac b/configure.ac
index a995f9d..edfab60 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15,7 +15,7 @@ dnl You should have received a copy of the GNU General Public License
 dnl along with this program.
 dnl If not, see [[http://www.gnu.org/licenses/][http://www.gnu.org/licenses/]].
 
-AC_INIT([tinmop],[0.4.1],[https://notabug.org/cage/tinmop/],[tinmop])
+AC_INIT([tinmop],[0.4.2],[https://notabug.org/cage/tinmop/],[tinmop])
 
 AM_INIT_AUTOMAKE([-Wall foreign])
 
diff --git a/tinmop.asd b/tinmop.asd
index a0166c6..0bca516 100644
--- a/tinmop.asd
+++ b/tinmop.asd
@@ -18,7 +18,7 @@
 (defsystem :tinmop
   :author      "cage"
   :license     "GPLv3"
-  :version     "0.4.1"
+  :version     "0.4.2"
   :pathname    "src"
   :serial      t
   :defsystem-depends-on ("cffi-grovel")