diff --git a/configure.ac b/configure.ac
index 8c1143390e3c09ff158e6dd532b3cce74622ea14..f49bed03af102b996deba5e2467cb73448a4b4dd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -580,6 +580,12 @@ AC_CHECK_FUNCS([getopt_long],[],
 	NEED_GETOPT=1])
 AC_FUNC_OBSTACK
 AM_CONDITIONAL(NEED_OBSTACK, [test ! "x${ac_cv_func_obstack}" = "xyes"])
+if test "x${ac_cv_func_obstack}" = "xyes"; then
+  HAVE_OBSTACK_H=1
+else
+  HAVE_OBSTACK_H=0
+fi
+AC_SUBST([HAVE_OBSTACK_H])
 
 GNUCOMPAT_INCLUDE_PATH='-I$(top_srcdir)/gnu-compat/'
 AC_SUBST([GNUCOMPAT_INCLUDE_PATH])