diff --git a/src/alire-boolean_trees.adb b/src/alire-boolean_trees.adb
index 7499f5a8..d918c88d 100644
--- a/src/alire-boolean_trees.adb
+++ b/src/alire-boolean_trees.adb
@@ -77,7 +77,7 @@ package body Alire.Boolean_Trees is
    -- Check --
    -----------
 
-   function Check (T : Tree; V : Value) return Boolean is
+   function Check (T : Tree; V : Value; If_Empty : Boolean := True) return Boolean is
 
       function Check (C : Trees.Cursor) return Boolean is
          N : constant Node := Trees.Element (C);
@@ -95,7 +95,11 @@ package body Alire.Boolean_Trees is
       end Check;
 
    begin
-      return Check (Trees.First_Child (T.Root));
+      if T.Is_Empty then
+         return If_Empty;
+      else
+         return Check (Trees.First_Child (T.Root));
+      end if;
    end Check;
 
    ---------------------
diff --git a/src/alire-boolean_trees.ads b/src/alire-boolean_trees.ads
index b79bfe64..8526f009 100644
--- a/src/alire-boolean_trees.ads
+++ b/src/alire-boolean_trees.ads
@@ -37,7 +37,7 @@ package Alire.Boolean_Trees with Preelaborate is
 
    --  Tree evaluation
 
-   function Check (T : Tree; V : Value) return Boolean;
+   function Check (T : Tree; V : Value; If_Empty : Boolean := True) return Boolean;
 
    --  Access
 
diff --git a/src/alire-properties-platform.ads b/src/alire-properties-platform.ads
index 01a32ee8..771ed70c 100644
--- a/src/alire-properties-platform.ads
+++ b/src/alire-properties-platform.ads
@@ -2,6 +2,14 @@ with Alire.Platforms;
 
 package Alire.Properties.Platform with Preelaborate is
 
+   function Compiler_Is (C : Platforms.Compilers) return Vector;
+
+   function Distribution_Is (D : Platforms.Distributions) return Vector;
+
+   function System_Is (V : Platforms.Operating_Systems) return Vector;
+
+   --  The following packages declare types used elsewhere so they have to be public  --
+
    package Compilers is new Values (Platforms.Compilers,
                                     Platforms.Compilers'IMage);
 
@@ -9,21 +17,17 @@ package Alire.Properties.Platform with Preelaborate is
                                         Platforms.Distributions'Image);
 
    package Operating_Systems is new Values (Platforms.Operating_Systems,
-                                           Platforms.Operating_Systems'Image);
-
---     function Current return Vector;
-   --  FIXME this will eventually have to go into Alr
+                                            Platforms.Operating_Systems'Image);
 
 private
 
-   function System_Is (V : Platforms.Operating_Systems) return Vector is
-     (+Operating_Systems.New_Property (V));
-
    function Compiler_Is (C : Platforms.Compilers) return Vector is
      (+Compilers.New_Property (C));
 
---     function Current return Vector is
---       (Compiler_Is (Alire.Compilers.Compiler) and
---          System_Is (Alire.Operating_Systems.Current));
+   function Distribution_Is (D : Platforms.Distributions) return Vector is
+     (+Distributions.New_Property (D));
+
+   function System_Is (V : Platforms.Operating_Systems) return Vector is
+     (+Operating_Systems.New_Property (V));
 
 end Alire.Properties.Platform;