diff --git a/src/signal_handler.c b/src/signal_handler.c
index 4e47b65f4df76dd7f9058df1d0c0357a000dfb40..83f411899c95185d63adfae129692ea32d0a513b 100644
--- a/src/signal_handler.c
+++ b/src/signal_handler.c
@@ -22,7 +22,7 @@
 #include "builtin_functions.h"
 #include <signal.h>
 
-RCSID("$Id: signal_handler.c,v 1.50 1998/04/21 14:19:34 grubba Exp $");
+RCSID("$Id: signal_handler.c,v 1.51 1998/04/21 16:09:42 grubba Exp $");
 
 #ifdef HAVE_PASSWD_H
 # include <passwd.h>
@@ -70,6 +70,11 @@ RCSID("$Id: signal_handler.c,v 1.50 1998/04/21 14:19:34 grubba Exp $");
 
 /* #define PROC_DEBUG */
 
+/* Added so we are able to patch older versions of Pike. */
+#ifndef add_ref
+#define add_ref(X)	((X)->refs++)
+#endif /* add_ref */
+
 extern int fd_from_object(struct object *o);
 
 static struct svalue signal_callbacks[MAX_SIGNALS];