diff --git a/drivers/mtd/mtd_config.c b/drivers/mtd/mtd_config.c
index 75ad692f54d..1f5bf6d8d0e 100644
--- a/drivers/mtd/mtd_config.c
+++ b/drivers/mtd/mtd_config.c
@@ -77,8 +77,8 @@ struct mtdconfig_struct_s
 {
   FAR struct mtd_dev_s *mtd;  /* Contained MTD interface */
   sem_t        exclsem;       /* Supports mutual exclusion */
-  uint32_t     blocksize :14; /* Size of blocks in contained MTD */
-  uint32_t     erasesize :18; /* Size of erase block  in contained MTD */
+  uint32_t     blocksize;     /* Size of blocks in contained MTD */
+  uint32_t     erasesize;     /* Size of erase block  in contained MTD */
   size_t       nblocks;       /* Number of blocks available */
   size_t       neraseblocks;  /* Number of erase blocks available */
   off_t        readoff;       /* Read offset (for hexdump) */