diff --git a/src/filo-blockdev.adb b/src/filo-blockdev.adb
index 44f79bd..6581c40 100644
--- a/src/filo-blockdev.adb
+++ b/src/filo-blockdev.adb
@@ -1,7 +1,7 @@
 package body FILO.Blockdev is
 
    procedure Read
-      (Buffer  : in out Buffer_Type;
+      (Buffer  :    out Buffer_Type;
        Offset  : in     Blockdev_Offset;
        Success :    out Boolean)
    with