diff --git a/lib/prefix.c b/lib/prefix.c
index 56539fc..2e594aa 100644
--- a/lib/prefix.c
+++ b/lib/prefix.c
@@ -738,11 +738,11 @@
 #ifdef HAVE_IPV6
 /* Utility function for making IPv6 address string. */
 const char *
-inet6_ntoa (struct in6_addr *addr)
+inet6_ntoa (struct in6_addr addr)
 {
   static char buf[INET6_ADDRSTRLEN];
 
-  inet_ntop (AF_INET6, addr, buf, INET6_ADDRSTRLEN);
+  inet_ntop (AF_INET6, &addr, buf, INET6_ADDRSTRLEN);
   return buf;
 }
 #endif /* HAVE_IPV6 */