diff --git a/shells/why3-dev/flake.nix b/shells/why3-dev/flake.nix
index 06ebb8a..017cb55 100644
--- a/shells/why3-dev/flake.nix
+++ b/shells/why3-dev/flake.nix
@@ -13,7 +13,10 @@
     {
       devShells."${system}".default =
         let
-          pkgs = import nixpkgs { inherit system; };
+          pkgs = import nixpkgs {
+            inherit system;
+            config.allowUnfree = true;
+          };
           menhir-lsp = pkgs.callPackage ./menhir-lsp.nix (pkgs // pkgs.ocamlPackages);
         in
         pkgs.mkShell {
@@ -21,18 +24,20 @@
             # Build elements
             autoconf
             ocaml
-            ocamlPackages.ocaml-lsp
             ocamlPackages.findlib
             ocamlPackages.menhir
             ocamlPackages.menhirLib
             ocamlPackages.zarith
             ocamlPackages.lablgtk3
             ocamlPackages.lablgtk3-sourceview3
+            ocamlPackages.camlzip
 
-            # Available provers
-            # alt-ergo
+            # Provers
+            alt-ergo
             cvc5
             z3
+            # Development tooling
+            ocamlPackages.ocaml-lsp
             menhir-lsp
           ];
         };