diff --git a/lib/sockunion.h b/lib/sockunion.h
index 4531f62..15b97fc 100644
--- a/lib/sockunion.h
+++ b/lib/sockunion.h
@@ -86,6 +86,8 @@
 
 #define sockunion_family(X)  (X)->sa.sa_family
 
+#define sockunion2ip(X)      (X)->sin.sin_addr.s_addr
+
 /* Prototypes. */
 extern int str2sockunion (const char *, union sockunion *);
 extern const char *sockunion2str (union sockunion *, char *, size_t);