diff --git a/src/aarch64-linux-flush-dcache/userspace/reader.c b/src/aarch64-linux-flush-dcache/userspace/reader.c
index c8715d8..58853e9 100644
--- a/src/aarch64-linux-flush-dcache/userspace/reader.c
+++ b/src/aarch64-linux-flush-dcache/userspace/reader.c
@@ -1,7 +1,7 @@
 #include <stdbool.h>
 #include <stdatomic.h>
 #include <pthread.h>
-#include <time.h>
+#include <time.h>		// timespec, nanosleep
 #include <unistd.h>		// sysconf
 #include <stdio.h>		// printf
 #include <stdlib.h>		// exit