diff --git a/libraries/AP_HAL/AP_HAL_Boards.h b/libraries/AP_HAL/AP_HAL_Boards.h
index 600a7c5444..14bdc9c859 100644
--- a/libraries/AP_HAL/AP_HAL_Boards.h
+++ b/libraries/AP_HAL/AP_HAL_Boards.h
@@ -144,10 +144,6 @@
 #error "No CONFIG_HAL_BOARD_SUBTYPE set"
 #endif
 
-#ifndef HAL_OS_POSIX_IO
-#define HAL_OS_POSIX_IO 0
-#endif
-
 #ifndef HAL_OS_SOCKETS
 #define HAL_OS_SOCKETS 0
 #endif
diff --git a/libraries/AP_HAL/board/linux.h b/libraries/AP_HAL/board/linux.h
index 67faddea01..5709bbeb0b 100644
--- a/libraries/AP_HAL/board/linux.h
+++ b/libraries/AP_HAL/board/linux.h
@@ -3,7 +3,6 @@
 #define HAL_BOARD_NAME "Linux"
 #define HAL_CPU_CLASS HAL_CPU_CLASS_1000
 #define HAL_MEM_CLASS HAL_MEM_CLASS_1000
-#define HAL_OS_POSIX_IO 1
 #define HAL_OS_SOCKETS 1
 #define HAL_STORAGE_SIZE            16384
 #define HAL_STORAGE_SIZE_AVAILABLE  HAL_STORAGE_SIZE
diff --git a/libraries/AP_HAL/board/sitl.h b/libraries/AP_HAL/board/sitl.h
index 7bea9ad10e..ab3d0488fb 100644
--- a/libraries/AP_HAL/board/sitl.h
+++ b/libraries/AP_HAL/board/sitl.h
@@ -3,7 +3,6 @@
 #define HAL_BOARD_NAME "SITL"
 #define HAL_CPU_CLASS HAL_CPU_CLASS_1000
 #define HAL_MEM_CLASS HAL_MEM_CLASS_1000
-#define HAL_OS_POSIX_IO 1
 #define HAL_OS_SOCKETS 1
 
 #define AP_FLASHSTORAGE_TYPE 3
diff --git a/libraries/AP_HAL/examples/UART_test/UART_test.cpp b/libraries/AP_HAL/examples/UART_test/UART_test.cpp
index 6f0315be21..c4be9c305d 100644
--- a/libraries/AP_HAL/examples/UART_test/UART_test.cpp
+++ b/libraries/AP_HAL/examples/UART_test/UART_test.cpp
@@ -4,7 +4,7 @@
 
 #include <AP_HAL/AP_HAL.h>
 
-#if HAL_OS_POSIX_IO
+#if AP_FILESYSTEM_POSIX_ENABLED
 #include <stdio.h>
 #endif
 
@@ -61,7 +61,7 @@ void loop(void)
 
     // also do a raw printf() on some platforms, which prints to the
     // debug console
-#if HAL_OS_POSIX_IO
+#if AP_FILESYSTEM_POSIX_ENABLED
     ::printf("Hello on debug console at %.3f seconds\n", (double)(AP_HAL::millis() * 0.001f));
 #endif