diff --git a/ChangeLog b/ChangeLog
index 04fef5eff..fff7f9c07 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+20000314
+ - Include macro for IN6_IS_ADDR_V4MAPPED. Report from 
+   peter@frontierflying.com
+
 20000311
  - Detect RSAref
  - OpenBSD CVS change
diff --git a/defines.h b/defines.h
index 519ebbaa2..48e14fd25 100644
--- a/defines.h
+++ b/defines.h
@@ -3,9 +3,12 @@
 
 /* Necessary headers */
 
-#include <sys/types.h> 
+#include <sys/types.h> /* For [u]intxx_t */
+
 #include <sys/socket.h> /* For SHUT_XXXX */
 
+#include <netinet/in.h> /* For IPv6 macros */
+
 #ifdef HAVE_SYS_BITYPES_H
 # include <sys/bitypes.h> /* For u_intXX_t */
 #endif 
@@ -234,6 +237,12 @@ typedef unsigned int size_t;
 # define __P(x) x
 #endif
 
+#if !defined(IN6_IS_ADDR_V4MAPPED)
+# define IN6_IS_ADDR_V4MAPPED(a) \
+	((((uint32_t *) (a))[0] == 0) && (((uint32_t *) (a))[1] == 0) && \
+	 (((uint32_t *) (a))[2] == htonl (0xffff)))
+#endif /* !defined(IN6_IS_ADDR_V4MAPPED) */
+
 #if !defined(__GNUC__) || (__GNUC__ < 2)
 # define __attribute__(x)
 #endif /* !defined(__GNUC__) || (__GNUC__ < 2) */