diff --git a/libc/include/netinet/in6.h b/libc/include/netinet/in6.h
index ae20f83..44b3e3e 100644
--- a/libc/include/netinet/in6.h
+++ b/libc/include/netinet/in6.h
@@ -89,7 +89,7 @@
   (IN6_IS_ADDR_MULTICAST(a) && (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_GLOBAL))
 
 #define IN6_ARE_ADDR_EQUAL(a, b) \
-  (memcmp(&(a)->s6_addr[0], &(b)->s6_addr[0], sizeof(struct in6_addr)) == 0)
+  (__builtin_memcmp(&(a)->s6_addr[0], &(b)->s6_addr[0], sizeof(struct in6_addr)) == 0)
 
 #define INET6_ADDRSTRLEN 46