diff --git a/targets/TARGET_STM/rtc_api.c b/targets/TARGET_STM/rtc_api.c
index 2b9b31a769..0f851a2e52 100644
--- a/targets/TARGET_STM/rtc_api.c
+++ b/targets/TARGET_STM/rtc_api.c
@@ -288,6 +288,7 @@ int rtc_isenabled(void)
 
 void rtc_synchronize(void)
 {
+    RtcHandle.Instance = RTC;
     if (HAL_RTC_WaitForSynchro(&RtcHandle) != HAL_OK) {
         error("rtc_synchronize error\n");
     }
@@ -298,6 +299,7 @@ void rtc_synchronize(void)
 static void RTC_IRQHandler(void)
 {
     /*  Update HAL state */
+    RtcHandle.Instance = RTC;
     HAL_RTCEx_WakeUpTimerIRQHandler(&RtcHandle);
     /* In case of registered handler, call it. */
     if (irq_handler) {
@@ -339,6 +341,7 @@ void rtc_set_wake_up_timer(uint32_t delta)
     NVIC_SetVector(RTC_WKUP_IRQn, (uint32_t)RTC_IRQHandler);
     NVIC_EnableIRQ(RTC_WKUP_IRQn);
 
+    RtcHandle.Instance = RTC;
     if (HAL_RTCEx_SetWakeUpTimer_IT(&RtcHandle, 0xFFFF & WakeUpCounter, WakeUpClock[DivIndex-1]) != HAL_OK) {
         error("rtc_set_wake_up_timer init error (%d)\n", DivIndex);
     }
@@ -346,6 +349,7 @@ void rtc_set_wake_up_timer(uint32_t delta)
 
 void rtc_deactivate_wake_up_timer(void)
 {
+    RtcHandle.Instance = RTC;
     HAL_RTCEx_DeactivateWakeUpTimer(&RtcHandle);
 }