diff --git a/cores/esp32/esp32-hal-uart.c b/cores/esp32/esp32-hal-uart.c
index e4432f5110f..c2065e806c4 100644
--- a/cores/esp32/esp32-hal-uart.c
+++ b/cores/esp32/esp32-hal-uart.c
@@ -497,6 +497,8 @@ uart_t *uartBegin(
     log_v("UART%d not installed. Starting installation", uart_nr);
   }
   uart_config_t uart_config;
+  memset(&uart_config, 0, sizeof(uart_config_t));
+  uart_config.flags.backup_before_sleep = false;  // new flag from IDF v5.3
   uart_config.data_bits = (config & 0xc) >> 2;
   uart_config.parity = (config & 0x3);
   uart_config.stop_bits = (config & 0x30) >> 4;