diff --git a/src/drivers/px4io/px4io.cpp b/src/drivers/px4io/px4io.cpp
index 9812ea497d..22d7072330 100644
--- a/src/drivers/px4io/px4io.cpp
+++ b/src/drivers/px4io/px4io.cpp
@@ -1095,8 +1095,10 @@ PX4IO::io_set_rc_config()
 	 * assign RC_MAP_ROLL/PITCH/YAW/THROTTLE to the canonical
 	 * controls.
 	 */
+
+	/* fill the mapping with an error condition triggering value */
 	for (unsigned i = 0; i < _max_rc_input; i++)
-		input_map[i] = -1;
+		input_map[i] = UINT16_MAX;
 
 	/*
 	 * NOTE: The indices for mapped channels are 1-based
@@ -1128,12 +1130,6 @@ PX4IO::io_set_rc_config()
 	if ((ichan >= 0) && (ichan < (int)_max_rc_input))
 		input_map[ichan - 1] = 4;
 
-	ichan = 5;
-
-	for (unsigned i = 0; i < _max_rc_input; i++)
-		if (input_map[i] == -1)
-			input_map[i] = ichan++;
-
 	/*
 	 * Iterate all possible RC inputs.
 	 */
diff --git a/src/modules/px4iofirmware/registers.c b/src/modules/px4iofirmware/registers.c
index 7ef1aa3091..b0922f4d69 100644
--- a/src/modules/px4iofirmware/registers.c
+++ b/src/modules/px4iofirmware/registers.c
@@ -602,7 +602,7 @@ registers_set_one(uint8_t page, uint8_t offset, uint16_t value)
 				if (conf[PX4IO_P_RC_CONFIG_DEADZONE] > 500) {
 					count++;
 				}
-				if (conf[PX4IO_P_RC_CONFIG_ASSIGNMENT] >= PX4IO_RC_MAPPED_CONTROL_CHANNELS) {
+				if ((int)(conf[PX4IO_P_RC_CONFIG_ASSIGNMENT]) < 0 || conf[PX4IO_P_RC_CONFIG_ASSIGNMENT] >= PX4IO_RC_MAPPED_CONTROL_CHANNELS) {
 					count++;
 				}