diff --git a/fs/driver/fs_blockpartition.c b/fs/driver/fs_blockpartition.c
index 05f28091377..d4c195f5b37 100644
--- a/fs/driver/fs_blockpartition.c
+++ b/fs/driver/fs_blockpartition.c
@@ -44,8 +44,8 @@ struct part_struct_s
 {
   FAR struct inode *parent;
   size_t sectorsize;
-  size_t firstsector;
-  size_t nsectors;
+  off_t firstsector;
+  off_t nsectors;
 };
 
 /****************************************************************************
@@ -318,7 +318,7 @@ static int part_unlink(FAR struct inode *inode)
 
 int register_blockpartition(FAR const char *partition,
                             mode_t mode, FAR const char *parent,
-                            size_t firstsector, size_t nsectors)
+                            off_t firstsector, off_t nsectors)
 {
   FAR struct part_struct_s *dev;
   struct geometry geo;
diff --git a/fs/driver/fs_mtdpartition.c b/fs/driver/fs_mtdpartition.c
index e4399b15074..655846b858f 100644
--- a/fs/driver/fs_mtdpartition.c
+++ b/fs/driver/fs_mtdpartition.c
@@ -61,7 +61,7 @@
 
 int register_mtdpartition(FAR const char *partition,
                           mode_t mode, FAR const char *parent,
-                          off_t firstblock, size_t nblocks)
+                          off_t firstblock, off_t nblocks)
 {
   FAR struct mtd_dev_s *part;
   FAR struct inode *mtd;
diff --git a/include/nuttx/fs/fs.h b/include/nuttx/fs/fs.h
index 45b670d45c3..81b12299543 100644
--- a/include/nuttx/fs/fs.h
+++ b/include/nuttx/fs/fs.h
@@ -597,7 +597,7 @@ int register_blockdriver(FAR const char *path,
 #ifndef CONFIG_DISABLE_MOUNTPOINT
 int register_blockpartition(FAR const char *partition,
                             mode_t mode, FAR const char *parent,
-                            size_t firstsector, size_t nsectors);
+                            off_t firstsector, off_t nsectors);
 #endif
 
 /****************************************************************************
@@ -674,7 +674,7 @@ int register_mtddriver(FAR const char *path, FAR struct mtd_dev_s *mtd,
 #ifdef CONFIG_MTD
 int register_mtdpartition(FAR const char *partition,
                           mode_t mode, FAR const char *parent,
-                          off_t firstblock, size_t nblocks);
+                          off_t firstblock, off_t nblocks);
 #endif
 
 /****************************************************************************