diff --git a/epicardium/modules/rtc.c b/epicardium/modules/rtc.c
index b07fb6fcc3925e4a52b80b6f7feb3294dcf181f8..24cf783ccb8ea0675bec10317ec8a11d8eb674c7 100644
--- a/epicardium/modules/rtc.c
+++ b/epicardium/modules/rtc.c
@@ -44,7 +44,7 @@ uint64_t epic_rtc_get_milliseconds(void)
 	while (RTC_GetTime(&sec, &subsec) == E_BUSY) {
 		vTaskDelay(pdMS_TO_TICKS(4));
 	}
-	return subsec * 1000ULL / 4096 + sec * 1000ULL;
+	return (subsec * 1000ULL + 999ULL) / 4096 + sec * 1000ULL;
 }
 
 void epic_rtc_set_milliseconds(uint64_t milliseconds)