diff --git a/configure.ac b/configure.ac
index 27f1463..9b16da7 100644
--- guile-2.0.9/configure.ac
+++ guile-2.0.9/configure.ac
@@ -741,7 +741,9 @@ AC_CHECK_HEADERS([assert.h crt_externs.h])
 #   truncate - not in mingw
 #   isblank - available as a GNU extension or in C99
 #   _NSGetEnviron - Darwin specific
-#   strcoll_l, newlocale - GNU extensions (glibc), also available on Darwin
+#   strcoll_l, strtol_l, strtod_l, nl_langinfo_l, toupper_l, tolower_l,
+#       newlocale - GNU/POSIX locale APIs used together by libguile/i18n.c;
+#       if some are missing, Guile must fall back to the compatibility path
 #   fork - unavailable on Windows
 #   utimensat - posix.1-2008
 #   sched_getaffinity, sched_setaffinity - GNU extensions (glibc)
@@ -756,7 +758,8 @@ AC_CHECK_FUNCS([DINFINITY DQNAN cexp chsize clog clog10 ctermid		\
   strptime symlink sync sysconf tcgetpgrp tcsetpgrp uname waitpid	\
   strdup system usleep atexit on_exit chown link fcntl ttyname getpwent	\
   getgrent kill getppid getpgrp fork setitimer getitimer strchr strcmp	\
-  index bcopy memcpy rindex truncate unsetenv isblank _NSGetEnviron	\
+  index bcopy memcpy rindex truncate unsetenv isblank _NSGetEnviron      \
+  nl_langinfo_l strtod_l strtol_l tolower_l toupper_l			\
   strcoll strcoll_l newlocale utimensat sched_getaffinity		\
   sched_setaffinity sendfile])

diff --git a/libguile/i18n.c b/libguile/i18n.c
index 09524e6..8b9534a 100644
--- guile-2.0.9/libguile/i18n.c
+++ guile-2.0.9/libguile/i18n.c
@@ -40,7 +40,10 @@
 #include <unicase.h>
 #include <unistr.h>
 
-#if (defined HAVE_NEWLOCALE) && (defined HAVE_STRCOLL_L)
+#if defined HAVE_NEWLOCALE && defined HAVE_NL_LANGINFO_L            \
+  && defined HAVE_STRCOLL_L && defined HAVE_STRTOD_L               \
+  && defined HAVE_STRTOL_L && defined HAVE_TOLOWER_L               \
+  && defined HAVE_TOUPPER_L
 /* The GNU thread-aware locale API is documented in ``Thread-Aware Locale
    Model, a Proposal'', by Ulrich Drepper: