diff --git a/os/hal/ports/STM32/LLD/RTCv2/rtc_lld.c b/os/hal/ports/STM32/LLD/RTCv2/rtc_lld.c
index 8e0cde83c..940abef7e 100644
--- a/os/hal/ports/STM32/LLD/RTCv2/rtc_lld.c
+++ b/os/hal/ports/STM32/LLD/RTCv2/rtc_lld.c
@@ -310,7 +310,7 @@ void rtc_lld_init(void) {
     rtc_enter_init();
 
     RTCD1.rtc->CR   = 0;
-    RTCD1.rtc->ISR  = 0;
+    RTCD1.rtc->ISR  = RTC_ISR_INIT;     /* Clearing all but RTC_ISR_INIT.   */
     RTCD1.rtc->PRER = STM32_RTC_PRER_BITS;
     RTCD1.rtc->PRER = STM32_RTC_PRER_BITS;
 
diff --git a/readme.txt b/readme.txt
index d21baad23..5682306cb 100644
--- a/readme.txt
+++ b/readme.txt
@@ -75,6 +75,7 @@
 
 *** 3.0.0p4 ***
 - HAL: New DAC driver implementation for STM32F4xx.
+- HAL: Fixed STM32 RTC PRER Register not being set in init (bug #590).
 - HAL: Fixed STM32F334 does not have an EXT18 interrupt (bug #588).
 - HAL: Fixed STM32L1xx USB is missing disconnect/connect macros (bug #587).
 - HAL: Fixed wrong vector number for STM32L1xx USB (bug #586).