diff --git a/boards/auav/x21/nuttx-config/Kconfig b/boards/auav/x21/nuttx-config/Kconfig
new file mode 100644
index 0000000000..f9eca7479a
--- /dev/null
+++ b/boards/auav/x21/nuttx-config/Kconfig
@@ -0,0 +1,5 @@
+# Hack to ensure ARCH_MATH_H is kept
+config BOARD_HAVE_MATH_H
+	bool "Provide ARCH math.h (selects ARCH_HAVE_MATH_H)"
+	default y
+	select ARCH_HAVE_MATH_H
diff --git a/boards/auav/x21/nuttx-config/drivers/Kconfig b/boards/auav/x21/nuttx-config/drivers/Kconfig
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/boards/auav/x21/nuttx-config/nsh/defconfig b/boards/auav/x21/nuttx-config/nsh/defconfig
index e1349f9b5a..3f71ac2d9b 100644
--- a/boards/auav/x21/nuttx-config/nsh/defconfig
+++ b/boards/auav/x21/nuttx-config/nsh/defconfig
@@ -1,3 +1,10 @@
+#
+# This file is autogenerated: PLEASE DO NOT EDIT IT.
+#
+# You can use "make menuconfig" to make any modifications to the installed .config file.
+# You can then do "make savedefconfig" to generate a new defconfig file that includes your
+# modifications.
+#
 # CONFIG_DISABLE_OS_API is not set
 # CONFIG_DISABLE_PSEUDOFS_OPERATIONS is not set
 # CONFIG_MMCSD_HAVE_CARDDETECT is not set
@@ -16,8 +23,11 @@
 # CONFIG_NSH_DISABLE_TIME is not set
 # CONFIG_STM32_CCMEXCLUDE is not set
 CONFIG_ARCH="arm"
+CONFIG_ARCH_BOARD_CUSTOM=y
 CONFIG_ARCH_BOARD_CUSTOM_DIR="../nuttx-config"
+CONFIG_ARCH_BOARD_CUSTOM_DIR_RELPATH=y
 CONFIG_ARCH_BOARD_CUSTOM_NAME="px4"
+CONFIG_ARCH_CHIP="stm32"
 CONFIG_ARCH_CHIP_STM32=y
 CONFIG_ARCH_CHIP_STM32F427V=y
 CONFIG_ARCH_INTERRUPTSTACK=512