diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/defaults_normal.h b/libraries/AP_HAL_ChibiOS/hwdef/scripts/defaults_normal.h
index 718da256e0..82d108d902 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/defaults_normal.h
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/defaults_normal.h
@@ -10,9 +10,18 @@
 #define HAL_BOARD_LOG_DIRECTORY "/APM/LOGS"
 #endif
 
+// a similar define is present in AP_HAL_Boards.h:
+#ifndef HAL_OS_FATFS_IO
+#define HAL_OS_FATFS_IO 0
+#endif
+
+#ifndef AP_TERRAIN_AVAILABLE
+// enable terrain only if there's an SD card available:
+#define AP_TERRAIN_AVAILABLE HAL_OS_FATFS_IO
+#endif
+
+#if AP_TERRAIN_AVAILABLE
 #ifndef HAL_BOARD_TERRAIN_DIRECTORY
 #define HAL_BOARD_TERRAIN_DIRECTORY "/APM/TERRAIN"
 #endif
-
-// enable terrain only if there's an SD card available:
-#define AP_TERRAIN_AVAILABLE HAL_OS_FATFS_IO
+#endif  // AP_TERRAIN_AVAILABLE