diff --git a/asli.nix b/asli.nix
index e7c34f44..843109d6 100644
--- a/asli.nix
+++ b/asli.nix
@@ -21,7 +21,7 @@ ocamlPackages.buildDunePackage {
   doCheck = lib.versionAtLeast ocaml.version "4.09";
 
   configurePhase = ''
-    sed -i 's|`opam config var ott:share`|${pkgs.ott.out + "/share/ott"}|' ./libASL/dune 
+    export ASLI_OTT=${pkgs.ott.out + "/share/ott"}
     mkdir -p $out/asl
     cp -rv prelude.asl mra_tools tests $out/asl
   '';
diff --git a/aslp.nix b/aslp.nix
index 08c2bc7d..b72f1110 100644
--- a/aslp.nix
+++ b/aslp.nix
@@ -11,6 +11,8 @@
       ASL_PATH=${asli}/asl
       cd ${asli}/bin
       makeBinaryWrapper "$(pwd)/asli" $out/bin/aslp \
+        --append-flags --prelude \
+        --append-flags $ASL_PATH/prelude.asl \
         --append-flags $ASL_PATH/prelude.asl \
         --append-flags $ASL_PATH/mra_tools/arch/regs.asl \
         --append-flags $ASL_PATH/mra_tools/types.asl \
diff --git a/bin/asli.ml b/bin/asli.ml
index 944f4da6..c9906af9 100644
--- a/bin/asli.ml
+++ b/bin/asli.ml
@@ -19,6 +19,7 @@ module TC     = Tcheck
 module PP     = Asl_parser_pp
 module AST    = Asl_ast
 
+let opt_prelude : string ref = ref "prelude.asl"
 let opt_filenames : string list ref = ref []
 let opt_print_version = ref false
 let opt_verbose = ref false
@@ -284,6 +285,7 @@ let options = Arg.align ([
     ( "-x", Arg.Set_int opt_debug_level,      "       Debugging output");
     ( "-v", Arg.Set opt_verbose,              "       Verbose output");
     ( "--version", Arg.Set opt_print_version, "       Print version");
+    ( "--prelude", Arg.Set_string opt_prelude,"       ASL prelude file (default: ./prelude.asl)");
 ] )
 
 let version = "ASL 0.2.0 alpha"
@@ -311,7 +313,7 @@ let main () =
     else begin
         if !opt_verbose then List.iter print_endline banner;
         if !opt_verbose then print_endline "\nType :? for help";
-        let t  = LoadASL.read_file "prelude.asl" true !opt_verbose in
+        let t  = LoadASL.read_file !opt_prelude true !opt_verbose in
         let ts = List.map (fun filename ->
             if Utils.endswith filename ".spec" then begin
                 LoadASL.read_spec filename !opt_verbose
diff --git a/libASL/dune b/libASL/dune
index f0a8b500..8197d9b6 100644
--- a/libASL/dune
+++ b/libASL/dune
@@ -10,7 +10,7 @@
    (progn
      (run ott -aux_style_rules false -tex_wrap true -quotient_rules false -i asl.ott -o asl_parser_head.mly -o asl_lexer.mll -o asl_ast.ml)
      (run mv asl_parser_head_pp.ml asl_parser_pp.ml)
-     (with-stdout-to asl_parser_tail.mly (bash "grep -v '^%%' `opam config var ott:share`/menhir_library_extra.mly"))
+     (with-stdout-to asl_parser_tail.mly (bash "OTT=${ASLI_OTT:-$(opam config var ott:share)};  grep -v '^%%' $OTT/menhir_library_extra.mly"))
      (with-stdout-to asl_parser.mly (run cat asl_parser_head.mly asl_parser_tail.mly)))))
 
 (library
diff --git a/shell.nix b/shell.nix
new file mode 100644
index 00000000..ebb7f415
--- /dev/null
+++ b/shell.nix
@@ -0,0 +1,20 @@
+{ pkgs ? import <nixpkgs> {} }:
+pkgs.mkShell {
+  packages = [ pkgs.opam pkgs.ocaml pkgs.ott pkgs.ocamlPackages.merlin pkgs.ocamlPackages.ocaml-lsp pkgs.ocamlformat ];
+
+  inputsFrom = [ pkgs.asli ];
+
+  shellHook = ''
+    export DEBUG=1
+    export OPAMSWITCH=nix-shell-asli
+    CAML_LD_PREV=$CAML_LD_LIBRARY_PATH
+
+    opam init --no-setup
+    opam switch create $OPAMSWITCH ocaml-system
+    eval $(opam env)
+
+    export ASLI_OTT=${pkgs.ott}/share/ott
+
+    export CAML_LD_LIBRARY_PATH=$CAML_LD_PREV:$CAML_LD_LIBRARY_PATH
+  '';
+}