diff --git a/ChangeLog b/ChangeLog
index b7942d4..ce70d26 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2000-04-06  Ben Elliston  <bje@redhat.com>
+
+	* config.guess: Define _HPUX_SOURCE for the HP-UX test program.
+	From Bruno Haible <haible@ilog.fr>.
+
 2000-04-06  Ben Elliston  <bje@redhat.com>
 
 	* config.guess: Detect Apple's Darwin operating system.
diff --git a/config.guess b/config.guess
index a6291c6..9e42606 100755
--- a/config.guess
+++ b/config.guess
@@ -458,6 +458,8 @@ EOF
 	    9000/[34]?? )         HP_ARCH=m68k ;;
 	    9000/[678][0-9][0-9])
               sed 's/^              //' << EOF >$dummy.c
+
+              #define _HPUX_SOURCE
               #include <stdlib.h>
               #include <unistd.h>