diff --git a/src/system.c b/src/system.c
--- a/src/system.c
+++ b/src/system.c
@@ -49,7 +49,7 @@ void sysclk_init(void)
     RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
     HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0);
 
-    PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART1|RCC_PERIPHCLK_I2C1;
+    PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART1|RCC_PERIPHCLK_I2C1|RCC_PERIPHCLK_RTC;
     PeriphClkInit.Usart1ClockSelection = RCC_USART1CLKSOURCE_SYSCLK; //RCC_USART1CLKSOURCE_PCLK1;
     PeriphClkInit.I2c1ClockSelection = RCC_I2C1CLKSOURCE_SYSCLK;
     PeriphClkInit.RTCClockSelection = RCC_RTCCLKSOURCE_LSI;