diff --git a/src/fs-filo.ads b/src/fs-filo.ads
index 43b6cef..12132e3 100644
--- a/src/fs-filo.ads
+++ b/src/fs-filo.ads
@@ -1,4 +1,5 @@
 with Interfaces.C;
+with System;
 
 package FS.FILO is
 
@@ -13,12 +14,13 @@
       (sector : Interfaces.C.unsigned_long;
        byte_offset : Interfaces.C.unsigned_long;
        byte_len : Interfaces.C.unsigned_long;
-       buf : ... )
+       buf : System.Address)
       return Interfaces.C.int
       with
          SPARK_Mode => Off,
          Import => True,
-         Conversion => C;
+         Convention => C,
+         External_Name => "devopen";
    
 
 end FS.FILO;