diff --git a/os_dep/linux/ioctl_cfg80211.c b/os_dep/linux/ioctl_cfg80211.c
old mode 100755
new mode 100644
index e7e8930..b3a5066
--- a/os_dep/linux/ioctl_cfg80211.c
+++ b/os_dep/linux/ioctl_cfg80211.c
@@ -686,7 +686,11 @@ static int rtw_cfg80211_sync_iftype(_adapter *adapter)
 
 static u64 rtw_get_systime_us(void)
 {
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 39))
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4, 20, 0))
+	struct timespec ts;
+	getboottime(&ts);
+	return ((u64)ts.tv_sec * 1000000) + ts.tv_nsec / 1000;
+#elif (LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 39))
 	struct timespec ts;
 	get_monotonic_boottime(&ts);
 	return ((u64)ts.tv_sec * 1000000) + ts.tv_nsec / 1000;