Index: openacs-4/packages/acs-lang/tcl/locale-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-lang/tcl/locale-procs.tcl,v
diff -u -r1.51.2.13 -r1.51.2.14
--- openacs-4/packages/acs-lang/tcl/locale-procs.tcl	26 Jun 2022 19:38:47 -0000	1.51.2.13
+++ openacs-4/packages/acs-lang/tcl/locale-procs.tcl	18 Aug 2022 14:58:58 -0000	1.51.2.14
@@ -530,9 +530,19 @@
 } {
     if { $site_wide_p } {
         set locale [lang::user::site_wide_locale]
+
         if { $locale eq "" } {
             set locale [lang::system::site_wide_locale]
         }
+
+        #
+        # Fallback to en_US when no locale is found or is not one of
+        # those we support.
+        #
+        if { $locale eq "" || $locale ni [lang::system::get_locales]} {
+            set locale en_US
+        }
+
         return $locale
     }