diff --git a/system-environment/config.nix b/system-environment/config.nix
index cbf2178..2a6949f 100644
--- a/system-environment/config.nix
+++ b/system-environment/config.nix
@@ -27,7 +27,13 @@ in
 
         # Ada/+Spark & Rust tools
         alire
-        gnat
+        gnat15
+        gnat15Packages.gprbuild
+        gnat15Packages.gpr2
+        gnat15Packages.gnatprove
+        gnat15Packages.gnatcoll-core
+        gnat15Packages.gnatcoll-readline
+        gnat15Packages.gnatcoll-python3
         rustc
         cargo
     ];