diff --git a/os/hal/platforms/STM32/USARTv1/serial_lld.c b/os/hal/platforms/STM32/USARTv1/serial_lld.c
index 9a9596424..eb344ebc0 100644
--- a/os/hal/platforms/STM32/USARTv1/serial_lld.c
+++ b/os/hal/platforms/STM32/USARTv1/serial_lld.c
@@ -161,7 +161,7 @@ static void serve_interrupt(SerialDriver *sdp) {
     chSysLockFromIsr();
     chnAddFlagsI(sdp, SD_BREAK_DETECTED);
     chSysUnlockFromIsr();
-    u->SR &= ~USART_SR_LBD;
+    u->SR = ~USART_SR_LBD;
   }
 
   /* Data available.*/
@@ -194,8 +194,8 @@ static void serve_interrupt(SerialDriver *sdp) {
     chSysLockFromIsr();
     chnAddFlagsI(sdp, CHN_TRANSMISSION_END);
     chSysUnlockFromIsr();
-    u->CR1 = cr1 & ~USART_CR1_TCIE;
-    u->SR &= ~USART_SR_TC;
+    u->CR1 = cr1 & ~(USART_CR1_TXEIE | USART_CR1_TCIE);
+    u->SR = ~USART_SR_TC;
   }
 }