diff --git a/src/filo-fs-ext2.ads b/src/filo-fs-ext2.ads
index 32b1940..ba47aef 100644
--- a/src/filo-fs-ext2.ads
+++ b/src/filo-fs-ext2.ads
@@ -45,6 +45,7 @@
 
    -- maximum block size is 64KiB (2^16):
    subtype Log_Block_Size is Positive range 10 .. 16;
+   subtype Block_Size is Natural range 2 ** Log_Block_Size'First .. 2 ** Log_Block_Size'Last;
    subtype Max_Block_Index is Index_Type range 0 .. 2 ** Log_Block_Size'Last - 1;
 
    -- Minimum ext2 block size is 1KiB (two 512B blocks)
@@ -85,7 +86,8 @@
       S : State;
       Part_Len             : Partition_Length := 0;
       First_Data_Block     : FSBlock_Offset := 0;
-      Block_Size_Bits      : Log_Block_Size := 10;
+      Block_Size_Bits      : Log_Block_Size := Log_Block_Size'First;
+      Block_Size           : Ext2.Block_Size := Ext2.Block_Size'First;
       Inodes_Per_Group     : Inode_Index := Inode_Index'First;
       Inode_Size           : Ext2.Inode_Size := Ext2.Inode_Size'First;
       Desc_Size            : Ext2.Desc_Size := Ext2.Desc_Size'First;