diff -rN -u old-mailutils-3.15/mail/util.c new-mailutils-3.15/mail/util.c
--- old-mailutils-3.15/mail/util.c	2023-02-20 14:10:45.412646572 +0000
+++ new-mailutils-3.15/mail/util.c	2023-02-20 14:10:45.412646572 +0000
@@ -1223,12 +1223,15 @@
     {
       struct mu_lc_all lc_all = { .flags = 0 };
       char *tmp = getenv ("LC_ALL");
-      if (!tmp)
+      if (!tmp || !strlen (tmp))
 	tmp = getenv ("LANG");
 
       if (tmp && mu_parse_lc_all (tmp, &lc_all, MU_LC_CSET) == 0)
 	{
-	  charset = mu_strdup (lc_all.charset);
+	  if (lc_all.charset)
+	    charset = mu_strdup (lc_all.charset);
+	  else
+	    charset = NULL;
 	  mu_lc_all_free (&lc_all);
 	}
       else