Index: src/natools-string_slices.adb
==================================================================
--- src/natools-string_slices.adb
+++ src/natools-string_slices.adb
@@ -1,7 +1,7 @@
 ------------------------------------------------------------------------------
--- Copyright (c) 2013, Natacha Porté                                        --
+-- Copyright (c) 2013-2016, Natacha Porté                                   --
 --                                                                          --
 -- Permission to use, copy, modify, and distribute this software for any    --
 -- purpose with or without fee is hereby granted, provided that the above   --
 -- copyright notice and this permission notice appear in all copies.        --
 --                                                                          --
@@ -14,11 +14,11 @@
 -- OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.           --
 ------------------------------------------------------------------------------
 
 package body Natools.String_Slices is
 
-   use type String_Refs.Reference;
+   use type String_Refs.Immutable_Reference;
 
 
    -----------------------------
    -- String_Range primitives --
    -----------------------------

Index: src/natools-string_slices.ads
==================================================================
--- src/natools-string_slices.ads
+++ src/natools-string_slices.ads
@@ -1,7 +1,7 @@
 ------------------------------------------------------------------------------
--- Copyright (c) 2013, Natacha Porté                                        --
+-- Copyright (c) 2013-2016, Natacha Porté                                   --
 --                                                                          --
 -- Permission to use, copy, modify, and distribute this software for any    --
 -- purpose with or without fee is hereby granted, provided that the above   --
 -- copyright notice and this permission notice appear in all copies.        --
 --                                                                          --
@@ -184,11 +184,11 @@
       Storage_Pools.Access_In_Default_Pool'Storage_Pool,
       Storage_Pools.Access_In_Default_Pool'Storage_Pool);
 
    type Slice is tagged record
       Bounds : String_Range := (1, 0);
-      Ref : String_Refs.Reference;
+      Ref : String_Refs.Immutable_Reference;
    end record;
 
    Null_Slice : constant Slice := ((1, 0), Ref => <>);
 
 end Natools.String_Slices;