diff --git a/hal/targets/hal/TARGET_STM/TARGET_STM32F4/rtc_api.c b/hal/targets/hal/TARGET_STM/TARGET_STM32F4/rtc_api.c
index 2f40051381..2a34e5c834 100644
--- a/hal/targets/hal/TARGET_STM/TARGET_STM32F4/rtc_api.c
+++ b/hal/targets/hal/TARGET_STM/TARGET_STM32F4/rtc_api.c
@@ -182,6 +182,7 @@ time_t rtc_read(void)
     timeinfo.tm_hour = timeStruct.Hours;
     timeinfo.tm_min  = timeStruct.Minutes;
     timeinfo.tm_sec  = timeStruct.Seconds;
+    timeinfo.tm_isdst  = -1;
 
     // Convert to timestamp
     time_t t = mktime(&timeinfo);