diff --git a/lib/prefix.h b/lib/prefix.h
index a2cdfe96fb..45e6368463 100644
--- a/lib/prefix.h
+++ b/lib/prefix.h
@@ -230,13 +230,8 @@ extern const char *prefix_family_str (const struct prefix *);
 extern int prefix_blen (const struct prefix *);
 extern int str2prefix (const char *, struct prefix *);
 
-/*
- * 8 groups of 4 bytes of hexadecimal + 7 seperators is 39
- * /128 = 4 bytes
- * Null = 1 byte
- * 39 + 4 + 1 = 44 bytes
- */
-#define PREFIX2STR_BUFFER  44
+#define PREFIX2STR_BUFFER  PREFIX_STRLEN
+
 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 *);