diff --git a/src/alire-os_lib.adb b/src/alire-os_lib.adb
new file mode 100644
index 00000000..71db0f2d
--- /dev/null
+++ b/src/alire-os_lib.adb
@@ -0,0 +1,20 @@
+with GNAT.OS_Lib;
+
+package body Alire.OS_Lib is
+
+   ----------------
+   -- Exe_Suffix --
+   ----------------
+
+   function Exe_Suffix return String is
+      --  Shenanigans needed to stay preelaborable
+      use GNAT.OS_Lib;
+
+      Suffix : String_Access := Get_Executable_Suffix;
+   begin
+      return S : constant String := Suffix.all do
+         Free (Suffix);
+      end return;
+   end Exe_Suffix;
+
+end Alire.OS_Lib;
diff --git a/src/alire-os_lib.ads b/src/alire-os_lib.ads
new file mode 100644
index 00000000..7f5a8887
--- /dev/null
+++ b/src/alire-os_lib.ads
@@ -0,0 +1,5 @@
+package Alire.OS_Lib with Preelaborate is
+
+   function Exe_Suffix return String;
+
+end Alire.OS_Lib;
diff --git a/src/alire-releases.adb b/src/alire-releases.adb
index 7d12dd76..c11e823f 100644
--- a/src/alire-releases.adb
+++ b/src/alire-releases.adb
@@ -18,7 +18,7 @@ package body Alire.Releases is
                   Label : Properties.Labeled.Label renames Properties.Labeled.Label (P);
                begin
                   if Label.Name = Executable then
-                     Exes.Append (Label.Value);
+                     Exes.Append (Label.Value & OS_Lib.Exe_Suffix);
                   end if;
                end;
             end if;
diff --git a/src/alire-releases.ads b/src/alire-releases.ads
index a5a648bc..cfb911b2 100644
--- a/src/alire-releases.ads
+++ b/src/alire-releases.ads
@@ -7,6 +7,8 @@ with Alire.Utils;
 
 with Semantic_Versioning;
 
+private with Alire.OS_Lib;
+
 package Alire.Releases with Preelaborate is
 
    subtype Dependencies is Alire.Dependencies.Vectors.Vector;
@@ -31,12 +33,15 @@ package Alire.Releases with Preelaborate is
    function Origin  (R : Release) return Origins.Origin;
 --     function Origin_Image (R : Release) return String;
 
+   function Default_Executable (R : Release) return String;
+   --  We encapsulate here the fixing of platform extension
+   
    function Executables (R : Release) return Utils.String_Vector;
    -- Only explicity declared ones
    
-   function Image (R : Release) return String;
-   -- Unique string built as name-version-id
-   function Unique_Folder (R : Release) return String renames Image;
+   function Image (R : Release) return Path_String;
+   -- Unique string built as name_version_id
+   function Unique_Folder (R : Release) return Path_String renames Image;
 
    function Milestone (R : Release) return Milestones.Milestone;
    
@@ -98,11 +103,13 @@ private
    
    function Milestone (R : Release) return Milestones.Milestone is 
       (Milestones.New_Milestone (R.Name, R.Version));
-
+   
+   function Default_Executable (R : Release) return String is
+      (R.Name & OS_Lib.Exe_Suffix);
+   
    function Is_Native (R : Release) return Boolean is (R.Native);  
    
-   --  FIXME: this should be OS-sanitized to be a valid path
-   function Image (R : Release) return String is
+   function Image (R : Release) return Path_String is
      (R.Name & "_" &
         Image (R.Version) & "_" &
       (if R.Origin.Id'Length <= 8 then R.Origin.Id 
diff --git a/src/alire-root_project.adb b/src/alire-root_project.adb
index 68f0c64e..624c0b50 100644
--- a/src/alire-root_project.adb
+++ b/src/alire-root_project.adb
@@ -37,9 +37,11 @@ package body Alire.Root_Project is
    is
       use Origins;
 
+      Descr : constant String := "working copy of " & Project;
       Rel : constant Releases.Release :=
               Alire.Releases.New_Release (Project,
-                                          "working copy of " & Project, -- FIXME might be too long
+                                          Descr (Descr'First .. Descr'First - 1 +
+                                              Natural'Min (Descr'Length, Max_Description_Length)),
                                           Version,
                                           New_Filesystem (Ada.Directories.Current_Directory),
                                           Depends_On,
diff --git a/src/alire.ads b/src/alire.ads
index 0f7ca09f..40a40f30 100644
--- a/src/alire.ads
+++ b/src/alire.ads
@@ -22,6 +22,10 @@ package Alire with Preelaborate is
    subtype Project_Description is String with Dynamic_Predicate =>
      Project_Description'Length <= Max_Description_Length;
 
+   subtype Path_String is String with Dynamic_Predicate =>
+     Path_String'Length > 0 and then
+     (for all C of Path_String => C in 'a' .. 'z' | 'A' .. 'Z' | '0' .. '9' | '_' | '.');
+
    ---------------
    --  LOGGING  --
    ---------------