diff --git a/drivers/timer/sandbox_timer.c b/drivers/timer/sandbox_timer.c
index 4b20af2..00a9944 100644
--- a/drivers/timer/sandbox_timer.c
+++ b/drivers/timer/sandbox_timer.c
@@ -18,7 +18,7 @@
 	sandbox_timer_offset += offset;
 }
 
-static int sandbox_timer_get_count(struct udevice *dev, unsigned long *count)
+static int sandbox_timer_get_count(struct udevice *dev, u64 *count)
 {
 	*count = os_get_nsec() / 1000 + sandbox_timer_offset * 1000;