diff --git a/app/flatpak-builtins-config.c b/app/flatpak-builtins-config.c
index eb5a8e9a..6fb40952 100644
--- a/app/flatpak-builtins-config.c
+++ b/app/flatpak-builtins-config.c
@@ -63,12 +63,79 @@ looks_like_a_language (const char *s)
   return TRUE;
 }
 
+static gboolean
+looks_like_a_region (const char *s)
+{
+  g_auto(GStrv) locale = g_strsplit (s, "_", 3);
+  int i;
+  int len;
+
+  if (!looks_like_a_language(locale[0]))
+    return FALSE;
+
+  if (locale[1] != NULL)
+    {
+      len = strlen (locale[1]);
+
+      // This can be either GB or Latn
+      if (len < 2 || len > 4)
+        return FALSE;
+
+      for (i = 0; i < len; i++)
+        {
+          if ((locale[2] == NULL) && (!g_ascii_isalpha (locale[1][i]) || !g_ascii_isupper (locale[1][i])))
+            return FALSE;
+          else if (!g_ascii_isalpha (locale[1][i]))
+            return FALSE;
+        }
+    }
+
+  if (g_strv_length (locale) > 2)
+    {
+      len = strlen (locale[2]);
+
+      if (len < 2 || len > 3)
+        return FALSE;
+
+      for (i = 0; i < len; i++)
+        {
+          if (!g_ascii_isalpha (locale[2][i]) || !g_ascii_isupper (locale[2][i]))
+            return FALSE;
+        }
+    }
+
+  return TRUE;
+}
+
+static char *
+parse_locale (const char *value, GError **error)
+{
+  g_auto(GStrv) strs = NULL;
+  int i;
+
+  strs = g_strsplit (value, ";", 0);
+  for (i = 0; strs[i]; i++)
+    {
+      if (!looks_like_a_language (strs[i]) && !looks_like_a_region (strs[i]))
+        {
+          flatpak_fail (error, _("'%s' does not look like a language/locale code"), strs[i]);
+          return NULL;
+        }
+    }
+
+  return g_strdup (value);
+}
+
 static char *
 parse_lang (const char *value, GError **error)
 {
   g_auto(GStrv) strs = NULL;
   int i;
 
+  if (strcmp (value, "*") == 0 ||
+      strcmp (value, "*all*") == 0)
+    return g_strdup ("");
+
   strs = g_strsplit (value, ";", 0);
   for (i = 0; strs[i]; i++)
     {
@@ -83,27 +150,17 @@ parse_lang (const char *value, GError **error)
 }
 
 static char *
-parse_special_lang (const char *value, GError **error)
-{
-  if (strcmp (value, "*") == 0 ||
-      strcmp (value, "*all*") == 0)
-    return g_strdup ("");
-
-  return parse_lang (value, error);
-}
-
-static char *
-print_lang (const char *value)
+print_locale (const char *value)
 {
   return g_strdup (value);
 }
 
 static char *
-print_special_lang (const char *value)
+print_lang (const char *value)
 {
   if (*value == 0)
     return g_strdup ("*all*");
-  return print_lang (value);
+  return g_strdup (value);
 }
 
 static char *
@@ -123,8 +180,8 @@ typedef struct
 } ConfigKey;
 
 ConfigKey keys[] = {
-  { "languages", parse_special_lang, print_special_lang, get_lang_default },
-  { "extra-languages", parse_lang, print_lang, NULL },
+  { "languages", parse_lang, print_lang, get_lang_default },
+  { "extra-languages", parse_locale, print_locale, NULL },
 };
 
 static ConfigKey *
diff --git a/common/flatpak-dir-private.h b/common/flatpak-dir-private.h
index 205d4e9b..2aca7adf 100644
--- a/common/flatpak-dir-private.h
+++ b/common/flatpak-dir-private.h
@@ -955,7 +955,9 @@ gboolean           flatpak_dir_resolve_p2p_refs (FlatpakDir         *self,
                                                  GError            **error);
 
 
+char ** flatpak_dir_get_default_locales (FlatpakDir *self);
 char ** flatpak_dir_get_default_locale_languages (FlatpakDir *self);
+char ** flatpak_dir_get_locales (FlatpakDir *self);
 char ** flatpak_dir_get_locale_languages (FlatpakDir *self);
 char ** flatpak_dir_get_locale_subpaths (FlatpakDir *self);
 
diff --git a/common/flatpak-dir.c b/common/flatpak-dir.c
index 2a89c4ef..6a68da43 100644
--- a/common/flatpak-dir.c
+++ b/common/flatpak-dir.c
@@ -14561,20 +14561,13 @@ flatpak_dir_get_config_strv (FlatpakDir *self, char *key)
   return NULL;
 }
 
-char **
-flatpak_dir_get_default_locale_languages (FlatpakDir *self)
+static void
+get_system_locales (FlatpakDir *self, GPtrArray *langs)
 {
-  g_autoptr(GPtrArray) langs = g_ptr_array_new_with_free_func (g_free);
   g_autoptr(GDBusProxy) localed_proxy = NULL;
   g_autoptr(GDBusProxy) accounts_proxy = NULL;
-  g_auto(GStrv) extra_languages = NULL;
 
-  extra_languages = flatpak_dir_get_config_strv (self, "xa.extra-languages");
-
-  if (flatpak_dir_is_user (self))
-    return sort_strv (flatpak_strv_merge (extra_languages, flatpak_get_current_locale_langs ()));
-
-  /* Then get the system default locales */
+  /* Get the system default locales */
   localed_proxy = get_localed_dbus_proxy ();
   if (localed_proxy != NULL)
     get_locale_langs_from_localed_dbus (localed_proxy, langs);
@@ -14584,12 +14577,67 @@ flatpak_dir_get_default_locale_languages (FlatpakDir *self)
   accounts_proxy = get_accounts_dbus_proxy ();
   if (accounts_proxy != NULL)
     get_locale_langs_from_accounts_dbus (accounts_proxy, langs);
-
   g_ptr_array_add (langs, NULL);
+}
+
+char **
+flatpak_dir_get_default_locales (FlatpakDir *self)
+{
+  g_autoptr(GPtrArray) langs = g_ptr_array_new_with_free_func (g_free);
+  g_auto(GStrv) extra_languages = NULL;
+
+  extra_languages = flatpak_dir_get_config_strv (self, "xa.extra-languages");
+
+  if (flatpak_dir_is_user (self))
+    return sort_strv (flatpak_strv_merge (extra_languages, flatpak_get_current_locale_langs ()));
+
+  /* Then get the system default locales */
+  get_system_locales (self, langs);
 
   return sort_strv (flatpak_strv_merge (extra_languages, (char **) langs->pdata));
 }
 
+char **
+flatpak_dir_get_default_locale_languages (FlatpakDir *self)
+{
+  g_autoptr(GPtrArray) langs = g_ptr_array_new_with_free_func (g_free);
+  g_auto(GStrv) extra_languages = NULL;
+  int i;
+
+  extra_languages = flatpak_dir_get_config_strv (self, "xa.extra-languages");
+  for (i = 0; extra_languages != NULL && extra_languages[i] != NULL; i++)
+    {
+       g_auto(GStrv) locales = g_strsplit (extra_languages[i], "_", -1);
+       g_free (extra_languages[i]);
+       extra_languages[i] = g_strdup (locales[0]);
+    }
+
+  if (flatpak_dir_is_user (self))
+    return sort_strv (flatpak_strv_merge (extra_languages, flatpak_get_current_locale_langs ()));
+
+  /* Then get the system default locales */
+  get_system_locales (self, langs);
+
+  return sort_strv (flatpak_strv_merge (extra_languages, (char **) langs->pdata));
+}
+
+char **
+flatpak_dir_get_locales (FlatpakDir *self)
+{
+  char **langs = NULL;
+
+  /* Fetch the list of languages specified by xa.languages - if this key is empty,
+   * this would mean that all languages are accepted. You can read the man for the
+   * flatpak-config section for more info.
+   */
+  langs = flatpak_dir_get_config_strv (self, "xa.languages");
+  if (langs)
+    return sort_strv (langs);
+
+  return flatpak_dir_get_default_locales (self);
+}
+
+
 char **
 flatpak_dir_get_locale_languages (FlatpakDir *self)
 {
diff --git a/common/flatpak-installation.c b/common/flatpak-installation.c
index 42e2af41..ad730671 100644
--- a/common/flatpak-installation.c
+++ b/common/flatpak-installation.c
@@ -1682,6 +1682,32 @@ flatpak_installation_get_default_languages (FlatpakInstallation  *self,
   return flatpak_dir_get_locale_languages (dir);
 }
 
+/**
+ * flatpak_installation_get_default_locales:
+ * @self: a #FlatpakInstallation
+ * @error: return location for a #GError
+ *
+ * Like flatpak_installation_get_default_languages() but includes region 
+ * information (e.g. en_US rather than en) which may be included in the 
+ * xa.extra-languages configuration.
+ *
+ * Returns: (array zero-terminated=1) (element-type utf8) (transfer full):
+ *   A possibly empty array of language and locale strings, or %NULL on error.
+ * Since: 1.5.1
+ */
+char **
+flatpak_installation_get_default_locales (FlatpakInstallation  *self,
+                                          GError              **error)
+{
+  g_autoptr(FlatpakDir) dir = NULL;
+
+  dir = flatpak_installation_get_dir (self, error);
+  if (dir == NULL)
+    return NULL;
+
+  return flatpak_dir_get_locales (dir);
+}
+
 /**
  * flatpak_installation_get_min_free_space_bytes:
  * @self: a #FlatpakInstallation
diff --git a/common/flatpak-installation.h b/common/flatpak-installation.h
index c97070ce..3baabad6 100644
--- a/common/flatpak-installation.h
+++ b/common/flatpak-installation.h
@@ -298,6 +298,8 @@ FLATPAK_EXTERN char *                flatpak_installation_get_config (FlatpakIns
                                                                       GError             **error);
 FLATPAK_EXTERN char **               flatpak_installation_get_default_languages (FlatpakInstallation  *self,
                                                                                  GError              **error);
+FLATPAK_EXTERN char **               flatpak_installation_get_default_locales (FlatpakInstallation  *self,
+                                                                               GError              **error);
 FLATPAK_EXTERN char *              flatpak_installation_load_app_overrides (FlatpakInstallation *self,
                                                                             const char          *app_id,
                                                                             GCancellable        *cancellable,
diff --git a/doc/flatpak-config.xml b/doc/flatpak-config.xml
index 5d05cb54..32d5420e 100644
--- a/doc/flatpak-config.xml
+++ b/doc/flatpak-config.xml
@@ -70,7 +70,8 @@
                 <listitem><para>
                    This key is used when languages is not set, and it defines extra locale
                    extensions on top of the system configured languages. The value is a
-                   semicolon-separated list of two-letter language codes.
+                   semicolon-separated list of two-letter language codes or locale identifiers
+                   (eg. en;en_DK;az_Latn_AZ).
                 </para></listitem>
             </varlistentry>
         </variablelist>
diff --git a/tests/testlibrary.c b/tests/testlibrary.c
index 0e017aed..c0cc4217 100644
--- a/tests/testlibrary.c
+++ b/tests/testlibrary.c
@@ -253,6 +253,22 @@ clean_languages (void)
   run_test_subprocess (argv, RUN_TEST_SUBPROCESS_DEFAULT);
 }
 
+static void
+configure_extra_languages (void)
+{
+  char *argv[] = { "flatpak", "config", "--user", "--set", "extra-languages", "de_DE", NULL };
+
+  run_test_subprocess (argv, RUN_TEST_SUBPROCESS_DEFAULT);
+}
+
+static void
+clean_extra_languages (void)
+{
+  char *argv[] = { "flatpak", "config", "--user", "--unset", "extra-languages", NULL };
+
+  run_test_subprocess (argv, RUN_TEST_SUBPROCESS_DEFAULT);
+}
+
 static void
 test_languages_config (void)
 {
@@ -273,18 +289,31 @@ test_languages_config (void)
   value = flatpak_installation_get_default_languages (inst, &error);
   g_assert_no_error (error);
   g_assert_cmpstr (value[0], ==, "en");
+  g_assert_null (value[1]);
 
-  res = flatpak_installation_set_config_sync (inst, "extra-languages", "en;pt", NULL, &error);
+  res = flatpak_installation_set_config_sync (inst, "extra-languages", "pt_BR;az_Latn_AZ;es", NULL, &error);
   g_assert_no_error (error);
   g_assert_true (res);
 
   value = flatpak_installation_get_default_languages (inst, &error);
   g_assert_no_error (error);
-  g_assert_cmpstr (value[0], ==, "en");
-  g_assert_cmpstr (value[1], ==, "pt");
-  g_assert_null (value[2]);
+  g_assert_cmpstr (value[0], ==, "az");
+  g_assert_cmpstr (value[1], ==, "en");
+  g_assert_cmpstr (value[2], ==, "es");
+  g_assert_cmpstr (value[3], ==, "pt");
+  g_assert_null (value[4]);
 
-  g_clear_pointer (&value, g_free);
+  g_clear_pointer (&value, g_strfreev);
+
+  value = flatpak_installation_get_default_locales (inst, &error);
+  g_assert_no_error (error);
+  g_assert_cmpstr (value[0], ==, "az_Latn_AZ");
+  g_assert_cmpstr (value[1], ==, "en");
+  g_assert_cmpstr (value[2], ==, "es");
+  g_assert_cmpstr (value[3], ==, "pt_BR");
+  g_assert_null (value[4]);
+
+  g_clear_pointer (&value, g_strfreev);
 
   res = flatpak_installation_set_config_sync (inst, "languages", "ar;es", NULL, &error);
   g_assert_no_error (error);
@@ -296,7 +325,8 @@ test_languages_config (void)
   g_assert_cmpstr (value[1], ==, "es");
   g_assert_null (value[2]);
 
-  g_clear_pointer (&value, g_free);
+  g_clear_pointer (&value, g_strfreev);
+  clean_extra_languages ();
   configure_languages ();
 }
 
@@ -1083,6 +1113,45 @@ test_list_remote_related_refs (void)
   g_assert_true (should_download);
   g_assert_true (should_delete);
   g_assert_false (should_autoprune);
+
+  // Make the test with extra-languages, instead of languages
+  clean_languages();
+  configure_extra_languages();
+
+  inst = flatpak_installation_new_user (NULL, &error);
+  g_assert_no_error (error);
+
+  refs = flatpak_installation_list_remote_related_refs_sync (inst, repo_name, app, NULL, &error);
+  g_assert_nonnull (refs);
+  g_assert_no_error (error);
+
+  g_assert_cmpint (refs->len, ==, 1);
+  ref = g_ptr_array_index (refs, 0);
+
+  g_assert_cmpstr (flatpak_ref_get_name (FLATPAK_REF (ref)), ==, "org.test.Hello.Locale");
+  g_assert_true (flatpak_related_ref_should_download (ref));
+  g_assert_true (flatpak_related_ref_should_delete (ref));
+  g_assert_false (flatpak_related_ref_should_autoprune (ref));
+  g_assert (g_strv_length ((char **) flatpak_related_ref_get_subpaths (ref)) == 2);
+  g_assert_cmpstr (flatpak_related_ref_get_subpaths (ref)[0], ==, "/de");
+  g_assert_cmpstr (flatpak_related_ref_get_subpaths (ref)[1], ==, "/en");
+
+  g_object_get (ref,
+                "subpaths", &subpaths,
+                "should-download", &should_download,
+                "should-delete", &should_delete,
+                "should-autoprune", &should_autoprune,
+                NULL);
+
+  g_assert (g_strv_length (subpaths) == 2);
+  g_assert_cmpstr (subpaths[0], ==, "/de");
+  g_assert_cmpstr (subpaths[1], ==, "/en");
+  g_assert_true (should_download);
+  g_assert_true (should_delete);
+  g_assert_false (should_autoprune);
+
+  configure_languages();
+  clean_extra_languages();
 }
 
 static void
@@ -3578,6 +3647,59 @@ test_list_installed_related_refs (void)
   g_assert_false (flatpak_related_ref_should_autoprune (ref));
   g_assert (g_strv_length ((char **) flatpak_related_ref_get_subpaths (ref)) == 1);
   g_assert_cmpstr (flatpak_related_ref_get_subpaths (ref)[0], ==, "/de");
+
+  // Make the test with extra-languages, instead of languages
+  clean_languages();
+  configure_extra_languages();
+  empty_installation (inst);
+
+  refs = flatpak_installation_list_installed_related_refs_sync (inst, repo_name, app, NULL, &error);
+  g_assert_error (error, FLATPAK_ERROR, FLATPAK_ERROR_NOT_INSTALLED);
+  g_assert_null (refs);
+  g_clear_error (&error);
+
+  iref = flatpak_installation_install (inst, repo_name, FLATPAK_REF_KIND_APP, "org.test.Hello", NULL, "master", NULL, NULL, NULL, &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (iref);
+  g_clear_object (&iref);
+
+  refs = flatpak_installation_list_installed_related_refs_sync (inst, repo_name, app, NULL, &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (refs);
+  g_assert_cmpint (refs->len, ==, 0);
+  g_clear_pointer (&refs, g_ptr_array_unref);
+
+  transaction = flatpak_transaction_new_for_installation (inst, NULL, &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (transaction);
+
+  res = flatpak_transaction_add_update (transaction, app, NULL, NULL, &error);
+  g_assert_no_error (error);
+  g_assert_true (res);
+
+  flatpak_transaction_run (transaction, NULL, &error);
+  g_assert_no_error (error);
+  g_assert_true (res);
+
+  g_clear_object (&transaction);
+
+  refs = flatpak_installation_list_installed_related_refs_sync (inst, repo_name, app, NULL, &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (refs);
+  g_assert_cmpint (refs->len, ==, 1);
+
+  ref = g_ptr_array_index (refs, 0);
+
+  g_assert_cmpstr (flatpak_ref_get_name (FLATPAK_REF (ref)), ==, "org.test.Hello.Locale");
+  g_assert_true (flatpak_related_ref_should_download (ref));
+  g_assert_true (flatpak_related_ref_should_delete (ref));
+  g_assert_false (flatpak_related_ref_should_autoprune (ref));
+  g_assert (g_strv_length ((char **) flatpak_related_ref_get_subpaths (ref)) == 2);
+  g_assert_cmpstr (flatpak_related_ref_get_subpaths (ref)[0], ==, "/de");
+  g_assert_cmpstr (flatpak_related_ref_get_subpaths (ref)[1], ==, "/en");
+
+  configure_languages();
+  clean_extra_languages();
 }
 
 static void