diff --git a/arch/arm/src/s32k3xx/s32k3xx_flexcan.c b/arch/arm/src/s32k3xx/s32k3xx_flexcan.c
index e27d2fcc377..99b3e12ebbd 100644
--- a/arch/arm/src/s32k3xx/s32k3xx_flexcan.c
+++ b/arch/arm/src/s32k3xx/s32k3xx_flexcan.c
@@ -845,6 +845,7 @@ static int s32k3xx_transmit(struct s32k3xx_driver_s *priv)
     (peak_tx_mailbox_index_ > mbi ? peak_tx_mailbox_index_ : mbi);
 
   union cs_e cs;
+  cs.cs = 0;
   cs.code = CAN_TXMB_DATAORREMOTE;
   struct mb_s *mb = &priv->tx[mbi];
   mb->cs.code = CAN_TXMB_INACTIVE;
@@ -889,6 +890,7 @@ static int s32k3xx_transmit(struct s32k3xx_driver_s *priv)
         }
 
       cs.rtr = frame->can_id & FLAGRTR ? 1 : 0;
+      cs.brs = frame->flags & CANFD_BRS ? 1 : 0;
 
       cs.dlc = g_len_to_can_dlc[frame->len];