diff --git a/extmod/vfs_fat.c b/extmod/vfs_fat.c
index 4af836b2d..024cecfe9 100644
--- a/extmod/vfs_fat.c
+++ b/extmod/vfs_fat.c
@@ -39,8 +39,8 @@
 #include "extmod/vfs_fat.h"
 #include "lib/timeutils/timeutils.h"
 
-#if _MAX_SS == _MIN_SS
-#define SECSIZE(fs) (_MIN_SS)
+#if FF_MAX_SS == FF_MIN_SS
+#define SECSIZE(fs) (FF_MIN_SS)
 #else
 #define SECSIZE(fs) ((fs)->ssize)
 #endif
@@ -111,7 +111,7 @@ STATIC mp_obj_t fat_vfs_mkfs(mp_obj_t bdev_in) {
     fs_user_mount_t *vfs = MP_OBJ_TO_PTR(fat_vfs_make_new(&mp_fat_vfs_type, 1, 0, &bdev_in));
 
     // make the filesystem
-    uint8_t working_buf[_MAX_SS];
+    uint8_t working_buf[FF_MAX_SS];
     FRESULT res = f_mkfs(&vfs->fatfs, FM_FAT | FM_SFD, 0, working_buf, sizeof(working_buf));
     if (res != FR_OK) {
         mp_raise_OSError(fresult_to_errno_table[res]);
@@ -363,7 +363,7 @@ STATIC mp_obj_t fat_vfs_statvfs(mp_obj_t vfs_in, mp_obj_t path_in) {
     t->items[6] = MP_OBJ_NEW_SMALL_INT(0); // f_ffree
     t->items[7] = MP_OBJ_NEW_SMALL_INT(0); // f_favail
     t->items[8] = MP_OBJ_NEW_SMALL_INT(0); // f_flags
-    t->items[9] = MP_OBJ_NEW_SMALL_INT(_MAX_LFN); // f_namemax
+    t->items[9] = MP_OBJ_NEW_SMALL_INT(FF_MAX_LFN); // f_namemax
 
     return MP_OBJ_FROM_PTR(t);
 }
@@ -383,7 +383,7 @@ STATIC mp_obj_t vfs_fat_mount(mp_obj_t self_in, mp_obj_t readonly, mp_obj_t mkfs
     // check if we need to make the filesystem
     FRESULT res = (self->flags & FSUSER_NO_FILESYSTEM) ? FR_NO_FILESYSTEM : FR_OK;
     if (res == FR_NO_FILESYSTEM && mp_obj_is_true(mkfs)) {
-        uint8_t working_buf[_MAX_SS];
+        uint8_t working_buf[FF_MAX_SS];
         res = f_mkfs(&self->fatfs, FM_FAT | FM_SFD, 0, working_buf, sizeof(working_buf));
     }
     if (res != FR_OK) {
diff --git a/extmod/vfs_fat_diskio.c b/extmod/vfs_fat_diskio.c
index fa013d278..e80d61241 100644
--- a/extmod/vfs_fat_diskio.c
+++ b/extmod/vfs_fat_diskio.c
@@ -42,8 +42,8 @@
 #include "lib/oofatfs/diskio.h"
 #include "extmod/vfs_fat.h"
 
-#if _MAX_SS == _MIN_SS
-#define SECSIZE(fs) (_MIN_SS)
+#if FF_MAX_SS == FF_MIN_SS
+#define SECSIZE(fs) (FF_MIN_SS)
 #else
 #define SECSIZE(fs) ((fs)->ssize)
 #endif
@@ -194,7 +194,7 @@ DRESULT disk_ioctl (
             } else {
                 *((WORD*)buff) = mp_obj_get_int(ret);
             }
-            #if _MAX_SS != _MIN_SS
+            #if FF_MAX_SS != FF_MIN_SS
             // need to store ssize because we use it in disk_read/disk_write
             vfs->fatfs.ssize = *((WORD*)buff);
             #endif