diff --git a/Tools/IO_Firmware/iofirmware_dshot_highpolh.bin b/Tools/IO_Firmware/iofirmware_dshot_highpolh.bin
index 5934290788ad0..ab6f6991365f7 100755
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diff --git a/Tools/IO_Firmware/iofirmware_dshot_lowpolh.bin b/Tools/IO_Firmware/iofirmware_dshot_lowpolh.bin
index c65751281d15a..d9bbf7d1595ac 100755
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diff --git a/Tools/IO_Firmware/iofirmware_f103_8MHz_highpolh.bin b/Tools/IO_Firmware/iofirmware_f103_8MHz_highpolh.bin
index adbf98f090cde..7d57720f09cdb 100755
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diff --git a/Tools/IO_Firmware/iofirmware_f103_8MHz_lowpolh.bin b/Tools/IO_Firmware/iofirmware_f103_8MHz_lowpolh.bin
index fce01bb26c29e..baf566a473b58 100755
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diff --git a/Tools/IO_Firmware/iofirmware_f103_dshot_highpolh.bin b/Tools/IO_Firmware/iofirmware_f103_dshot_highpolh.bin
index 2ba418de0788f..31946079ca86e 100755
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diff --git a/Tools/IO_Firmware/iofirmware_f103_dshot_lowpolh.bin b/Tools/IO_Firmware/iofirmware_f103_dshot_lowpolh.bin
index 1a0426c5761b6..d34ef4149ed9d 100755
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diff --git a/Tools/IO_Firmware/iofirmware_f103_highpolh.bin b/Tools/IO_Firmware/iofirmware_f103_highpolh.bin
index af9d068cd5ea5..b68ea0d2e93ac 100755
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diff --git a/Tools/IO_Firmware/iofirmware_f103_lowpolh.bin b/Tools/IO_Firmware/iofirmware_f103_lowpolh.bin
index 8db3cfaad172d..29cda52a000f7 100755
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diff --git a/Tools/IO_Firmware/iofirmware_highpolh.bin b/Tools/IO_Firmware/iofirmware_highpolh.bin
index 988375fa5d73c..409bf4fafe549 100755
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diff --git a/Tools/IO_Firmware/iofirmware_lowpolh.bin b/Tools/IO_Firmware/iofirmware_lowpolh.bin
index 059048670ef3f..604c15fe8161f 100755
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diff --git a/libraries/AP_IOMCU/AP_IOMCU.cpp b/libraries/AP_IOMCU/AP_IOMCU.cpp
index fefa91ebf0377..73f283532f2b9 100644
--- a/libraries/AP_IOMCU/AP_IOMCU.cpp
+++ b/libraries/AP_IOMCU/AP_IOMCU.cpp
@@ -346,7 +346,7 @@ void AP_IOMCU::thread_main(void)
         // update failsafe pwm
         if (pwm_out.failsafe_pwm_set != pwm_out.failsafe_pwm_sent) {
             uint8_t set = pwm_out.failsafe_pwm_set;
-            if (write_registers(PAGE_FAILSAFE_PWM, 0, IOMCU_MAX_CHANNELS, pwm_out.failsafe_pwm)) {
+            if (write_registers(PAGE_FAILSAFE_PWM, 0, IOMCU_MAX_RC_CHANNELS, pwm_out.failsafe_pwm)) {
                 pwm_out.failsafe_pwm_sent = set;
             }
         }
@@ -372,7 +372,7 @@ void AP_IOMCU::send_servo_out()
         if (rate.sbus_rate_hz == 0) {
             n = MIN(n, 8);
         } else {
-            n = MIN(n, IOMCU_MAX_CHANNELS);
+            n = MIN(n, IOMCU_MAX_RC_CHANNELS);
         }
         uint32_t now = AP_HAL::micros();
         if (now - last_servo_out_us >= 2000 || AP_BoardConfig::io_dshot()) {
diff --git a/libraries/AP_IOMCU/iofirmware/iofirmware.cpp b/libraries/AP_IOMCU/iofirmware/iofirmware.cpp
index 6e97fa4cf2714..545dfad9aac41 100644
--- a/libraries/AP_IOMCU/iofirmware/iofirmware.cpp
+++ b/libraries/AP_IOMCU/iofirmware/iofirmware.cpp
@@ -966,7 +966,7 @@ bool AP_IOMCU_FW::handle_code_write()
         }
         /* copy channel data */
         uint16_t i = 0, num_values = rx_io_packet.count;
-        while ((i < IOMCU_MAX_CHANNELS) && (num_values > 0)) {
+        while ((i < IOMCU_MAX_RC_CHANNELS) && (num_values > 0)) {
             /* XXX range-check value? */
             if (rx_io_packet.regs[i] != PWM_IGNORE_THIS_CHANNEL) {
                 reg_direct_pwm.pwm[i] = rx_io_packet.regs[i];
diff --git a/libraries/AP_IOMCU/iofirmware/iofirmware.h b/libraries/AP_IOMCU/iofirmware/iofirmware.h
index 824a2238e4220..6069b3cf2add1 100644
--- a/libraries/AP_IOMCU/iofirmware/iofirmware.h
+++ b/libraries/AP_IOMCU/iofirmware/iofirmware.h
@@ -93,17 +93,17 @@ class AP_IOMCU_FW {
 
     // PAGE_SERVO values
     struct {
-        uint16_t pwm[IOMCU_MAX_CHANNELS];
+        uint16_t pwm[IOMCU_MAX_RC_CHANNELS];    // size has to account for virtual channels via SBUS_OUT
     } reg_servo;
 
     // PAGE_DIRECT_PWM values
     struct {
-        uint16_t pwm[IOMCU_MAX_CHANNELS];
+        uint16_t pwm[IOMCU_MAX_RC_CHANNELS];
     } reg_direct_pwm;
 
     // PAGE_FAILSAFE_PWM
     struct {
-        uint16_t pwm[IOMCU_MAX_CHANNELS];
+        uint16_t pwm[IOMCU_MAX_RC_CHANNELS];
     } reg_failsafe_pwm;
 
     // output rates