diff --git a/src/configure.in b/src/configure.in
index 9596ed3906eb4d2a971e38561b58971b56ce9328..87b1a2fb7c295dffddd886bea649a1d4edc4c5e0 100644
--- a/src/configure.in
+++ b/src/configure.in
@@ -1,4 +1,4 @@
-AC_REVISION("$Id: configure.in,v 1.186 1998/05/17 20:37:55 grubba Exp $")
+AC_REVISION("$Id: configure.in,v 1.187 1998/05/17 22:57:57 grubba Exp $")
 AC_INIT(interpret.c)
 AC_CONFIG_HEADER(machine.h)
 
@@ -1747,6 +1747,20 @@ fi
 
 #############################################################################
 
+AC_MSG_CHECKING(for isgraph)
+AC_CACHE_VAL(pike_cv_func_isgraph, [ AC_COMPILE([
+#include <ctype.h>
+], [
+return(!isgraph('A'));
+], pike_cv_func_isgraph=yes, pike_cv_func_isgraph=no)
+])
+AC_MSG_RESULT($pike_cv_func_isgraph)
+if test "x$pike_cv_func_isgraph" = "xyes" ; then
+  AC_DEFINE(HAVE_ISGRAPH)
+else :; fi
+
+#############################################################################
+
 AC_MSG_CHECKING(for gcc function attributes)
 AC_CACHE_VAL(pike_cv_gcc_attributes,
 [