diff --git a/os/hal/include/can.h b/os/hal/include/can.h
index 234981448..1d8492d28 100644
--- a/os/hal/include/can.h
+++ b/os/hal/include/can.h
@@ -118,6 +118,11 @@ typedef enum {
  * @name    Macro Functions
  * @{
  */
+/**
+ * @bried   Converts a mailbox index to a bit mask.
+ */
+#define CAN_MAILBOX_TO_MASK(mbx) (1 << ((mbx) - 1))
+
 /**
  * @brief   Adds some flags to the CAN status mask.
  *
diff --git a/os/hal/platforms/STM32/can_lld.c b/os/hal/platforms/STM32/can_lld.c
index 7a6185c1f..89d1b25ac 100644
--- a/os/hal/platforms/STM32/can_lld.c
+++ b/os/hal/platforms/STM32/can_lld.c
@@ -137,7 +137,7 @@ static void can_lld_tx_handler(CANDriver *canp) {
   chSysLockFromIsr();
   while (chSemGetCounterI(&canp->txsem) < 0)
     chSemSignalI(&canp->txsem);
-  chEvtBroadcastI(&canp->txempty_event);
+  chEvtBroadcastFlagsI(&canp->txempty_event, CAN_MAILBOX_TO_MASK(1));
   chSysUnlockFromIsr();
 }
 
@@ -158,7 +158,7 @@ static void can_lld_rx0_handler(CANDriver *canp) {
     chSysLockFromIsr();
     while (chSemGetCounterI(&canp->rxsem) < 0)
       chSemSignalI(&canp->rxsem);
-    chEvtBroadcastI(&canp->rxfull_event);
+    chEvtBroadcastFlagsI(&canp->rxfull_event, CAN_MAILBOX_TO_MASK(1));
     chSysUnlockFromIsr();
   }
   if ((rf0r & CAN_RF0R_FOVR0) > 0) {