diff --git a/include/main.h b/include/main.h
index 3a843d8..2d52526 100644
--- a/include/main.h
+++ b/include/main.h
@@ -10,7 +10,7 @@
 #include "config_data.h"
 
 #define SW_VER "EA20"
-#define SW_DATE "11042023"
+#define SW_DATE "14042023"
 #define SW_KISS_PROTO	"A"
 
 #define SYSTICK_TICKS_PER_SECONDS 100
diff --git a/include/main_master_time.h b/include/main_master_time.h
index 20eb676..9be7a85 100644
--- a/include/main_master_time.h
+++ b/include/main_master_time.h
@@ -10,7 +10,7 @@
 
 #include <stdint.h>
 
-extern uint32_t master_time;
+extern volatile uint32_t master_time;
 
 inline uint32_t main_get_master_time(void) {
 	return master_time;
diff --git a/src/main.c b/src/main.c
index 7feca22..b996b42 100644
--- a/src/main.c
+++ b/src/main.c
@@ -164,7 +164,7 @@ const config_data_gsm_t * main_config_data_gsm = 0;
 #endif
 
 //! global variable incremented by the SysTick handler to measure time in miliseconds
-uint32_t master_time = 0;
+volatile uint32_t master_time = 0;
 
 //! current timestamp from RTC in NVM format
 uint32_t main_nvm_timestamp = 0;