diff --git a/os_dep/linux/ioctl_cfg80211.c b/os_dep/linux/ioctl_cfg80211.c
index 5f4a975..153dbd4 100755
--- a/os_dep/linux/ioctl_cfg80211.c
+++ b/os_dep/linux/ioctl_cfg80211.c
@@ -686,6 +686,7 @@ static int rtw_cfg80211_sync_iftype(_adapter *adapter)
 
 static u64 rtw_get_systime_us(void)
 {
+// Fix build error for Linux >= 4.19
 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 39))
 	struct timespec ts;
 	getboottime(&ts);