diff --git a/lib/prefix.h b/lib/prefix.h
index 7afe7a1..f2a2adf 100644
--- a/lib/prefix.h
+++ b/lib/prefix.h
@@ -151,6 +151,9 @@
 extern int str2prefix_ipv4 (const char *, struct prefix_ipv4 *);
 extern void apply_mask_ipv4 (struct prefix_ipv4 *);
 
+#define PREFIX_COPY_IPV4(DST, SRC)	\
+	*((struct prefix_ipv4 *)(DST)) = *((const struct prefix_ipv4 *)(SRC));
+
 extern int prefix_ipv4_any (const struct prefix_ipv4 *);
 extern void apply_classful_mask_ipv4 (struct prefix_ipv4 *);
 
@@ -172,6 +175,9 @@
 extern int str2prefix_ipv6 (const char *, struct prefix_ipv6 *);
 extern void apply_mask_ipv6 (struct prefix_ipv6 *);
 
+#define PREFIX_COPY_IPV6(DST, SRC)	\
+	*((struct prefix_ipv6 *)(DST)) = *((const struct prefix_ipv6 *)(SRC));
+
 extern int ip6_masklen (struct in6_addr);
 extern void masklen2ip6 (int, struct in6_addr *);