diff --git a/libc/include/netinet/in.h b/libc/include/netinet/in.h
index 0ebd926..7a4b6c7 100644
--- a/libc/include/netinet/in.h
+++ b/libc/include/netinet/in.h
@@ -38,6 +38,8 @@
 
 #define IPPORT_RESERVED  1024
 
+#define INET_ADDRSTRLEN 16
+
 extern int bindresvport (int sd, struct sockaddr_in *sin);
 
 static const struct in6_addr in6addr_any = IN6ADDR_ANY_INIT;