diff --git a/tests/sys/kern/socket_msg_trunc.c b/tests/sys/kern/socket_msg_trunc.c
--- a/tests/sys/kern/socket_msg_trunc.c
+++ b/tests/sys/kern/socket_msg_trunc.c
@@ -44,7 +44,7 @@
 check_recvmsg(int cs, int ss, struct sockaddr *sa, const size_t sizes[],
     size_t nsizes)
 {
-	char buf[4096];
+	char buf[9000];
 
 	memset(buf, 0xFF, sizeof(buf));
 	for (size_t i = 0; i < nsizes; i++) {
@@ -52,6 +52,8 @@
 		size_t sz = sizes[i];
 		char tbuf[1];
 
+		ATF_REQUIRE(sz <= sizeof(buf));
+
 		rc = sendto(cs, buf, sz, 0, sa, sa->sa_len);
 		ATF_REQUIRE_MSG(rc != -1, "sendto failed: %s", strerror(errno));
 		ATF_REQUIRE((size_t)rc == sz);