diff --git a/libraries/AP_HAL/HAL.cpp b/libraries/AP_HAL/HAL.cpp
index 280f1ab2ca..a2d1216d2b 100644
--- a/libraries/AP_HAL/HAL.cpp
+++ b/libraries/AP_HAL/HAL.cpp
@@ -17,7 +17,7 @@ AP_HAL::UARTDriver* AP_HAL::HAL::serial(uint8_t sernum) const
 {
     UARTDriver **uart_array = const_cast<UARTDriver**>(&uartA);
     // this mapping captures the historical use of uartB as SERIAL3
-    const uint8_t mapping[] = { 0, 2, 3, 1, 4, 5, 6, 7, 8 };
+    const uint8_t mapping[] = { 0, 2, 3, 1, 4, 5, 6, 7, 8, 9 };
     static_assert(sizeof(mapping) == num_serial, "num_serial must match mapping");
     if (sernum >= num_serial) {
         return nullptr;
diff --git a/libraries/AP_HAL/HAL.h b/libraries/AP_HAL/HAL.h
index 9d14ec3563..ae9a0861b7 100644
--- a/libraries/AP_HAL/HAL.h
+++ b/libraries/AP_HAL/HAL.h
@@ -29,6 +29,7 @@ public:
         AP_HAL::UARTDriver* _uartG, // extra2
         AP_HAL::UARTDriver* _uartH, // extra3
         AP_HAL::UARTDriver* _uartI, // extra4
+        AP_HAL::UARTDriver* _uartJ, // extra5
         AP_HAL::I2CDeviceManager* _i2c_mgr,
         AP_HAL::SPIDeviceManager* _spi,
         AP_HAL::QSPIDeviceManager* _qspi,
@@ -58,6 +59,7 @@ public:
         uartG(_uartG),
         uartH(_uartH),
         uartI(_uartI),
+        uartJ(_uartJ),
         i2c_mgr(_i2c_mgr),
         spi(_spi),
         qspi(_qspi),
@@ -115,6 +117,7 @@ private:
     AP_HAL::UARTDriver* uartG;
     AP_HAL::UARTDriver* uartH;
     AP_HAL::UARTDriver* uartI;
+    AP_HAL::UARTDriver* uartJ;
 
 public:
     AP_HAL::I2CDeviceManager* i2c_mgr;
@@ -140,5 +143,5 @@ public:
     // access to serial ports using SERIALn_ numbering
     UARTDriver* serial(uint8_t sernum) const;
 
-    static constexpr uint8_t num_serial = 9;
+    static constexpr uint8_t num_serial = 10;
 };