diff --git a/arch/arm/src/imxrt/imxrt_flexcan.c b/arch/arm/src/imxrt/imxrt_flexcan.c
index 2afc3700698..70288fa7d56 100644
--- a/arch/arm/src/imxrt/imxrt_flexcan.c
+++ b/arch/arm/src/imxrt/imxrt_flexcan.c
@@ -656,6 +656,7 @@ static int imxrt_transmit(struct imxrt_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 = flexcan_get_mb(priv, mbi);
   mb->cs.code = CAN_TXMB_INACTIVE;
@@ -698,6 +699,7 @@ static int imxrt_transmit(struct imxrt_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];