diff --git a/libc/dns/resolv/res_cache.c b/libc/dns/resolv/res_cache.c
index 9ca5419..dd77693 100644
--- a/libc/dns/resolv/res_cache.c
+++ b/libc/dns/resolv/res_cache.c
@@ -1915,7 +1915,7 @@
         hints.ai_family = PF_UNSPEC;
         hints.ai_socktype = SOCK_DGRAM; /*dummy*/
         hints.ai_flags = AI_NUMERICHOST;
-        sprintf(sbuf, "%u", NAMESERVER_PORT);
+        snprintf(sbuf, sizeof(sbuf), "%u", NAMESERVER_PORT);
 
         index = 0;
         for (i = 0; i < numservers && i < MAXNS; i++) {