diff --git a/src/fs-filo-vfs.ads b/src/fs-filo-vfs.ads
index ce5da18..95fa71d 100644
--- a/src/fs-filo-vfs.ads
+++ b/src/fs-filo-vfs.ads
@@ -9,20 +9,21 @@
    with procedure Mount (Success : out Boolean);
 
    with procedure Open (File_Path : String; Success : out Boolean);
-   with procedure Close;
+   with procedure Close with Convention => C;
 
-   with procedure Read (Buf : out Buffer_Type; Success : out Boolean);
+   with procedure Read (Buf : out Buffer_Type; Len : out Natural);
 
 package FS.FILO.VFS
 with
-   SPARK_Mode => Off
+   SPARK_Mode => Off,
+   Convention => C
 is
 
-   function C_Mount return int is (0);
+   function C_Mount return int;
 
-   function C_Open (File_Path : Strings.chars_ptr) return int is (0);
-   procedure C_Close is null;
+   function C_Open (File_Path : Strings.chars_ptr) return int;
+   procedure C_Close renames Close;
    
-   function C_Read (Buf : System.Address; Len : int) return int is (0);
+   function C_Read (Buf : System.Address; Len : int) return int;
 
 end FS.FILO.VFS;