diff --git a/libraries/MySensors/drivers/RF24/RF24.cpp b/libraries/MySensors/drivers/RF24/RF24.cpp
index 24b0a69..fc813f0 100644
--- a/libraries/MySensors/drivers/RF24/RF24.cpp
+++ b/libraries/MySensors/drivers/RF24/RF24.cpp
@@ -1168,7 +1168,7 @@ void RF24::writeAckPayload(uint8_t pipe, const void* buf, uint8_t len)
 
 bool RF24::isAckPayloadAvailable(void)
 {
-  return ! read_register(FIFO_STATUS) & _BV(RX_EMPTY);
+  return !(read_register(FIFO_STATUS) & _BV(RX_EMPTY));
 }
 
 /****************************************************************************/