diff --git a/src/drivers/px4fmu/fmu.cpp b/src/drivers/px4fmu/fmu.cpp
index 2486dc0488..4da54beed4 100644
--- a/src/drivers/px4fmu/fmu.cpp
+++ b/src/drivers/px4fmu/fmu.cpp
@@ -195,7 +195,7 @@ private:
 	unsigned	_num_outputs;
 	int		_class_instance;
 	int		_rcs_fd;
-	uint8_t _rcs_buf[SBUS_FRAME_SIZE];
+	uint8_t _rcs_buf[SBUS_BUFFER_SIZE * 2];
 
 	volatile bool	_initialized;
 	bool		_throttle_armed;
@@ -1281,7 +1281,7 @@ PX4FMU::cycle()
 	}
 
 	// read all available data from the serial RC input UART
-	int newBytes = ::read(_rcs_fd, &_rcs_buf[0], SBUS_FRAME_SIZE);
+	int newBytes = ::read(_rcs_fd, &_rcs_buf[0], sizeof(_rcs_buf) / sizeof(_rcs_buf[0]));
 
 	switch (_rc_scan_state) {
 	case RC_SCAN_SBUS: