diff --git a/lib/sensor_pzem.c b/lib/sensor_pzem.c
index 15291d9..f5ce861 100644
--- a/lib/sensor_pzem.c
+++ b/lib/sensor_pzem.c
@@ -176,7 +176,7 @@ struct sensor_pzem_measurement_t sensor_pzem_measurement_decode(void)
 /** USART interrupt service routine called when data has been transmitted or received */
 void USART_ISR(SENSOR_PZEM_USART)(void)
 {
-	if (usart_get_interrupt_source(USART(SENSOR_PZEM_USART), USART_SR_TXE)) { // data has been transmitted
+	if (usart_get_flag(USART(SENSOR_PZEM_USART), USART_SR_TXE)) { // data has been transmitted
 		if (tx_i<LENGTH(tx_buffer)) { // not all bytes transmitted
 			usart_send(USART(SENSOR_PZEM_USART),tx_buffer[tx_i++]); // transmit next byte
 		} else { // request transmitted
@@ -186,7 +186,7 @@ void USART_ISR(SENSOR_PZEM_USART)(void)
 
 		}
 	}
-	if (usart_get_interrupt_source(USART(SENSOR_PZEM_USART), USART_SR_RXNE)) { // data has been received
+	if (usart_get_flag(USART(SENSOR_PZEM_USART), USART_SR_RXNE)) { // data has been received
 		if (rx_i<LENGTH(rx_buffer)) { // receiving response
 			rx_buffer[rx_i++] = usart_recv(USART(SENSOR_PZEM_USART)); // put received byte in buffer
 			if (rx_i>=LENGTH(rx_buffer)) { // buffer full