diff --git a/m4/mbswidth.m4 b/m4/mbswidth.m4
index eaf552bf..158653c4 100644
--- a/m4/mbswidth.m4
+++ b/m4/mbswidth.m4
@@ -1,12 +1,11 @@
-#serial 7
+#serial 8
 
 dnl autoconf tests required for use of mbswidth.c
 dnl From Bruno Haible.
 
 AC_DEFUN([jm_PREREQ_MBSWIDTH],
 [
-  AC_REQUIRE([AC_HEADER_STDC])
-  AC_CHECK_HEADERS(limits.h stdlib.h string.h wchar.h wctype.h)
+  AC_CHECK_HEADERS(wchar.h wctype.h)
   AC_CHECK_FUNCS(isascii iswcntrl iswprint mbsinit wcwidth)
   jm_FUNC_MBRTOWC