diff --git a/os/hal/ports/STM32/LLD/RTCv2/hal_rtc_lld.c b/os/hal/ports/STM32/LLD/RTCv2/hal_rtc_lld.c
index a6c776d3a..09844f680 100644
--- a/os/hal/ports/STM32/LLD/RTCv2/hal_rtc_lld.c
+++ b/os/hal/ports/STM32/LLD/RTCv2/hal_rtc_lld.c
@@ -509,6 +509,7 @@ void rtcSTM32SetPeriodicWakeup(RTCDriver *rtcp, const RTCWakeup *wakeupspec) {
     osalDbgCheck(wakeupspec->wutr != 0x30000);
 
     rtcp->rtc->CR &= ~RTC_CR_WUTE;
+    rtcp->rtc->CR &= ~RTC_CR_WUTIE;
     while (!(rtcp->rtc->ISR & RTC_ISR_WUTWF))
       ;
     rtcp->rtc->WUTR = wakeupspec->wutr & 0xFFFF;
@@ -518,8 +519,8 @@ void rtcSTM32SetPeriodicWakeup(RTCDriver *rtcp, const RTCWakeup *wakeupspec) {
     rtcp->rtc->CR |= RTC_CR_WUTE;
   }
   else {
-    rtcp->rtc->CR &= ~RTC_CR_WUTIE;
     rtcp->rtc->CR &= ~RTC_CR_WUTE;
+    rtcp->rtc->CR &= ~RTC_CR_WUTIE;
   }
 
   /* Leaving a reentrant critical zone.*/
diff --git a/readme.txt b/readme.txt
index 0c303f2f1..ee17396ce 100644
--- a/readme.txt
+++ b/readme.txt
@@ -157,6 +157,8 @@
 - RT:  Merged RT4.
 - NIL: Merged NIL2.
 - NIL: Added STM32F7 demo.
+- HAL: Fixed problem in rtcSTM32SetPeriodicWakeup() (bug #821)(backported
+       to 16.1.8).
 - HAL: Fixed STM32 RTCv1 synchronization problem (bug #820)(backported
        to 16.1.8).
 - HAL: Fixed wrong clock source definition for LPTIM on STM32L0xx (bug #819)