diff --git a/src/alire-platforms.ads b/src/alire-platforms.ads
index ecdf494a..f91605ff 100644
--- a/src/alire-platforms.ads
+++ b/src/alire-platforms.ads
@@ -7,10 +7,12 @@ package Alire.Platforms with Preelaborate is
                       GNAT_GPL_2017);
 
    type Operating_Systems is (GNU_Linux,
-                              Windows);
+                              Windows,
+                              Unsupported);
 
    type Distributions is (Debian_Buster,
-                          Ubuntu_Artful);
+                          Ubuntu_Artful,
+                          Unsupported);
    --  Known flavors of OSs
    --  It turns out that Debian uses no numbers for its non-stable releases, so we'll prefer the codename
    --  These are important mostly to tie platform package names to releases