diff --git a/targets/f7/fatfs/user_diskio.c b/targets/f7/fatfs/user_diskio.c
index 85e5cad4f..963cb595f 100644
--- a/targets/f7/fatfs/user_diskio.c
+++ b/targets/f7/fatfs/user_diskio.c
@@ -9,7 +9,7 @@ static DRESULT driver_read(BYTE pdrv, BYTE* buff, DWORD sector, UINT count);
 static DRESULT driver_write(BYTE pdrv, const BYTE* buff, DWORD sector, UINT count);
 static DRESULT driver_ioctl(BYTE pdrv, BYTE cmd, void* buff);
 
-Diskio_drvTypeDef sd_fatfs_driver = {
+const Diskio_drvTypeDef sd_fatfs_driver = {
     driver_initialize,
     driver_status,
     driver_read,
diff --git a/targets/f7/fatfs/user_diskio.h b/targets/f7/fatfs/user_diskio.h
index 009a17d4b..2505de704 100644
--- a/targets/f7/fatfs/user_diskio.h
+++ b/targets/f7/fatfs/user_diskio.h
@@ -6,7 +6,7 @@ extern "C" {
 
 #include "fatfs/ff_gen_drv.h"
 
-extern Diskio_drvTypeDef sd_fatfs_driver;
+extern const Diskio_drvTypeDef sd_fatfs_driver;
 
 #ifdef __cplusplus
 }