diff --git a/subsys/modbus/modbus_serial.c b/subsys/modbus/modbus_serial.c
index 5e748b08beb..06e44bd2414 100644
--- a/subsys/modbus/modbus_serial.c
+++ b/subsys/modbus/modbus_serial.c
@@ -404,13 +404,15 @@ static void cb_handler_tx(struct modbus_context *ctx)
 static void uart_cb_handler(const struct device *dev, void *app_data)
 {
 	struct modbus_context *ctx = (struct modbus_context *)app_data;
-	struct modbus_serial_config *cfg = ctx->cfg;
+	struct modbus_serial_config *cfg;
 
 	if (ctx == NULL) {
 		LOG_ERR("Modbus hardware is not properly initialized");
 		return;
 	}
 
+	cfg = ctx->cfg;
+
 	while (uart_irq_update(cfg->dev) && uart_irq_is_pending(cfg->dev)) {
 
 		if (uart_irq_rx_ready(cfg->dev)) {