diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index bd6b3abdcec..ee378a6b157 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1813,8 +1813,8 @@ features:
    On some Unix systems (such as Linux), the following attributes may also be
    available:
 
-   * :attr:`st_blocks` - number of blocks allocated for file
-   * :attr:`st_blksize` - filesystem blocksize
+   * :attr:`st_blocks` - number of 512-byte blocks allocated for file
+   * :attr:`st_blksize` - filesystem blocksize for efficient file system I/O
    * :attr:`st_rdev` - type of device if an inode device
    * :attr:`st_flags` - user defined flags for file