diff --git a/libc/include/netinet/in.h b/libc/include/netinet/in.h
index 46e3543..b235e6e 100644
--- a/libc/include/netinet/in.h
+++ b/libc/include/netinet/in.h
@@ -54,7 +54,7 @@
 
 typedef uint16_t in_port_t;
 
-int bindresvport(int __fd, struct sockaddr_in* __sin);
+int bindresvport(int __fd, struct sockaddr_in* _Nullable __sin);
 
 #if __ANDROID_API__ >= 24
 extern const struct in6_addr in6addr_any __INTRODUCED_IN(24);