diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c
index c2e5f57..db66fd3 100644
--- a/arch/sandbox/cpu/os.c
+++ b/arch/sandbox/cpu/os.c
@@ -8,6 +8,7 @@
 #include <fcntl.h>
 #include <getopt.h>
 #include <stdio.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <termios.h>
@@ -136,7 +137,7 @@
 	usleep(usec);
 }
 
-u64 __attribute__((no_instrument_function)) os_get_nsec(void)
+uint64_t __attribute__((no_instrument_function)) os_get_nsec(void)
 {
 #if defined(CLOCK_MONOTONIC) && defined(_POSIX_MONOTONIC_CLOCK)
 	struct timespec tp;
diff --git a/include/os.h b/include/os.h
index 8665f70..950433d 100644
--- a/include/os.h
+++ b/include/os.h
@@ -11,6 +11,8 @@
 #ifndef __OS_H__
 #define __OS_H__
 
+#include <linux/types.h>
+
 struct sandbox_state;
 
 /**
@@ -116,7 +118,7 @@
  *
  * \return A monotonic increasing time scaled in nano seconds
  */
-u64 os_get_nsec(void);
+uint64_t os_get_nsec(void);
 
 /**
  * Parse arguments and update sandbox state.