diff --git a/src/modules/px4iofirmware/registers.c b/src/modules/px4iofirmware/registers.c
index f0c2cfd26d..ae7aec34e4 100644
--- a/src/modules/px4iofirmware/registers.c
+++ b/src/modules/px4iofirmware/registers.c
@@ -284,7 +284,7 @@ registers_set(uint8_t page, uint8_t offset, const uint16_t *values, unsigned num
 	case PX4IO_PAGE_DIRECT_PWM:
 
 		/* copy channel data */
-		while ((offset < PX4IO_CONTROL_CHANNELS) && (num_values > 0)) {
+		while ((offset < PX4IO_SERVO_COUNT) && (num_values > 0)) {
 
 			/* XXX range-check value? */
 			if (*values != PWM_IGNORE_THIS_CHANNEL) {