diff --git a/features/filesystem/fat/FATFileSystem.cpp b/features/filesystem/fat/FATFileSystem.cpp
index caf04a7da4..6ab567fedc 100644
--- a/features/filesystem/fat/FATFileSystem.cpp
+++ b/features/filesystem/fat/FATFileSystem.cpp
@@ -71,58 +71,6 @@ static int fat_error_remap(FRESULT res)
     }
 }
 
-void fat_filesystem_set_errno(FRESULT res)
-{
-    switch(res) {
-        case FR_OK:                     /* (0) Succeeded */
-            errno = 0;                  /* no error */
-            break;
-        case FR_DISK_ERR:               /* (1) A hard error occurred in the low level disk I/O layer */
-        case FR_NOT_READY:              /* (3) The physical drive cannot work */
-            errno = EIO;                /* I/O error */
-            break;
-        case FR_NO_FILE:                /* (4) Could not find the file */
-        case FR_NO_PATH:                /* (5) Could not find the path */
-        case FR_INVALID_NAME:           /* (6) The path name format is invalid */
-        case FR_INVALID_DRIVE:          /* (11) The logical drive number is invalid */
-        case FR_NO_FILESYSTEM:          /* (13) There is no valid FAT volume */
-            errno = ENOENT;             /* No such file or directory */
-            break;
-        case FR_DENIED:                 /* (7) Access denied due to prohibited access or directory full */
-            errno = EACCES;             /* Permission denied */
-            break;
-        case FR_EXIST:                  /* (8) Access denied due to prohibited access */
-            errno = EEXIST;             /* File exists */
-            break;
-        case FR_WRITE_PROTECTED:        /* (10) The physical drive is write protected */
-        case FR_LOCKED:                 /* (16) The operation is rejected according to the file sharing policy */
-            errno = EACCES;             /* Permission denied */
-            break;
-        case FR_INVALID_OBJECT:         /* (9) The file/directory object is invalid */
-            errno = EFAULT;             /* Bad address */
-            break;
-        case FR_NOT_ENABLED:            /* (12) The volume has no work area */
-            errno = ENXIO;              /* No such device or address */
-            break;
-        case FR_NOT_ENOUGH_CORE:        /* (17) LFN working buffer could not be allocated */
-            errno = ENOMEM;             /* Not enough space */
-            break;
-        case FR_TOO_MANY_OPEN_FILES:    /* (18) Number of open files > _FS_LOCK */
-            errno = ENFILE;             /* Too many open files in system */
-            break;
-        case FR_INVALID_PARAMETER:      /* (19) Given parameter is invalid */
-            errno = ENOEXEC;            /* Exec format error */
-            break;
-        case FR_INT_ERR:                /* (2) Assertion failed */
-        case FR_MKFS_ABORTED:           /* (14) The f_mkfs() aborted due to any parameter error */
-        case FR_TIMEOUT:                /* (15) Could not get a grant to access the volume within defined period */
-        default:
-            errno = EBADF;              /* Bad file number */
-            break;
-    }
-    return;
-}
-
 
 
 ////// Disk operations //////