diff --git a/lib/prefix.c b/lib/prefix.c
index 57cf12a..63742f3 100644
--- a/lib/prefix.c
+++ b/lib/prefix.c
@@ -760,14 +760,15 @@
   return 0;
 }
 
-int
-prefix2str (const struct prefix *p, char *str, int size)
+const char *
+prefix2str (union prefix46constptr pu, char *str, int size)
 {
+  const struct prefix *p = pu.p;
   char buf[BUFSIZ];
 
   inet_ntop (p->family, &p->u.prefix, buf, BUFSIZ);
   snprintf (str, size, "%s/%d", buf, p->prefixlen);
-  return 0;
+  return str;
 }
 
 struct prefix *
diff --git a/lib/prefix.h b/lib/prefix.h
index 404a63a..bc8aebc 100644
--- a/lib/prefix.h
+++ b/lib/prefix.h
@@ -129,6 +129,9 @@
 #define INET6_BUFSIZ 51
 #endif /* INET6_BUFSIZ */
 
+/* Maximum prefix string length (IPv6) */
+#define PREFIX_STRLEN 51
+
 /* Max bit/byte length of IPv4 address. */
 #define IPV4_MAX_BYTELEN    4
 #define IPV4_MAX_BITLEN    32
@@ -179,7 +182,7 @@
 extern const char *prefix_family_str (const struct prefix *);
 extern int prefix_blen (const struct prefix *);
 extern int str2prefix (const char *, struct prefix *);
-extern int prefix2str (const struct prefix *, char *, int);
+extern const char *prefix2str (union prefix46constptr, char *, int);
 extern int prefix_match (const struct prefix *, const struct prefix *);
 extern int prefix_same (const struct prefix *, const struct prefix *);
 extern int prefix_cmp (const struct prefix *, const struct prefix *);
diff --git a/lib/zclient.c b/lib/zclient.c
index 1e05d6d..71da87c 100644
--- a/lib/zclient.c
+++ b/lib/zclient.c
@@ -808,11 +808,11 @@
 	   else if (CHECK_FLAG(ifc->flags, ZEBRA_IFA_PEER))
 	     {
 	       /* carp interfaces on OpenBSD with 0.0.0.0/0 as "peer" */
-	       char buf[BUFSIZ];
-	       prefix2str (ifc->address, buf, sizeof(buf));
+	       char buf[PREFIX_STRLEN];
 	       zlog_warn("warning: interface %s address %s "
 		    "with peer flag set, but no peer address!",
-		    ifp->name, buf);
+		    ifp->name,
+		    prefix2str (ifc->address, buf, sizeof buf));
 	       UNSET_FLAG(ifc->flags, ZEBRA_IFA_PEER);
 	     }
 	 }