diff --git a/tests/sys/cddl/zfs/bin/file_write.c b/tests/sys/cddl/zfs/bin/file_write.c
index b1ef836879e6..07ba6503dff8 100644
--- a/tests/sys/cddl/zfs/bin/file_write.c
+++ b/tests/sys/cddl/zfs/bin/file_write.c
@@ -38,7 +38,7 @@ static unsigned char bigbuffer[BIGBUFFERSIZE];
  * See header file for defaults.
  */
 
-static void usage(void);
+static void usage(void) __dead2;
 static char *execname;
 
 int
diff --git a/tests/sys/netinet/libalias/perf.c b/tests/sys/netinet/libalias/perf.c
index f238846bdb16..07e73612a6dd 100644
--- a/tests/sys/netinet/libalias/perf.c
+++ b/tests/sys/netinet/libalias/perf.c
@@ -38,7 +38,7 @@
 #include "util.h"
 #include <alias.h>
 
-static void usage(void);
+static void usage(void) __dead2;
 
 #define	timevalcmp(tv, uv, cmp)			\
 	(((tv).tv_sec == (uv).tv_sec)		\