diff --git a/lib/libutil/tests/pidfile_test.c b/lib/libutil/tests/pidfile_test.c
index 9e516c35273..9bfa6754ce5 100644
--- a/lib/libutil/tests/pidfile_test.c
+++ b/lib/libutil/tests/pidfile_test.c
@@ -286,7 +286,8 @@ test_pidfile_relative(void)
 	fd = open(path, O_RDONLY);
 	if (fd < 0)
 		return (strerror(errno));
-	if (read(fd, pid, sizeof(pid)) < 0)
+	memset(pid, 0, sizeof(pid));
+	if (read(fd, pid, sizeof(pid) - 1) < 0)
 		return (strerror(errno));
 	if (atoi(pid) != getpid())
 		return ("pid mismatch");