diff --git a/firmware/chibios/os/hal/platforms/STM32/RTCv2/rtc_lld.c b/firmware/chibios/os/hal/platforms/STM32/RTCv2/rtc_lld.c
index e6df4beecc..d556398fa3 100644
--- a/firmware/chibios/os/hal/platforms/STM32/RTCv2/rtc_lld.c
+++ b/firmware/chibios/os/hal/platforms/STM32/RTCv2/rtc_lld.c
@@ -154,6 +154,8 @@ void rtc_lld_set_time(RTCDriver *rtcp, const RTCTime *timespec) {
 void rtc_lld_get_time(RTCDriver *rtcp, RTCTime *timespec) {
   (void)rtcp;
 
+  chDbgAssert(RTCD1.id_rtc == RTC, "RTC", "RTC");
+
   rtc_lld_apb1_sync();
 
 #if STM32_RTC_HAS_SUBSECONDS
diff --git a/firmware/util/efilib.cpp b/firmware/util/efilib.cpp
index 83f8683b8f..1a3779174c 100644
--- a/firmware/util/efilib.cpp
+++ b/firmware/util/efilib.cpp
@@ -13,8 +13,6 @@
 #include "datalogging.h"
 #include "histogram.h"
 
-#define _MAX_FILLER 11
-
 const char * boolToString(bool value) {
 	return value ? "Yes" : "No";
 }
@@ -118,6 +116,9 @@ int atoi(const char *string) {
 
 static char todofixthismesswithcopy[100];
 
+/**
+ * WARNING: due to implementation details specifid buffer should be at least size of '_MAX_FILLER'
+ */
 static char *ltoa_internal(char *p, long num, unsigned radix) {
 	int i;
 	char *q;
diff --git a/firmware/util/efilib.h b/firmware/util/efilib.h
index e49894d2f7..740eece8a0 100644
--- a/firmware/util/efilib.h
+++ b/firmware/util/efilib.h
@@ -11,6 +11,8 @@
 #include <stdint.h>
 #include "global.h"
 
+#define _MAX_FILLER 11
+
 // http://en.wikipedia.org/wiki/Endianness
 
 #define SWAP_UINT16(x) ((x) << 8) | ((x) >> 8)