diff --git a/src/lib/arith.ml b/src/lib/arith.ml
index 6e6d06b..7942f14 100644
--- a/src/lib/arith.ml
+++ b/src/lib/arith.ml
@@ -25,10 +25,16 @@ type expr =
 
 module Make (S : Types.State) = struct
   let eval initial_state expr =
+    let exception Abort of int in
     let lookup state s =
+      let s =
+        match String.get s 0 with
+        | '$' -> String.sub s 1 (String.length s - 1)
+        | (exception _) | _ -> s
+      in
       match S.lookup state ~param:s with
       | Some n when Option.is_some (int_of_string_opt n) -> int_of_string n
-      | _ -> 0
+      | _ -> raise (Abort 0)
     in
     let update state s i =
       match S.update state ~param:s (string_of_int i) with
@@ -54,5 +60,5 @@ module Make (S : Types.State) = struct
           let state, v1 = calc state e1 in
           if Int.equal v1 Int.zero then calc state e3 else calc state e2
     in
-    calc initial_state expr
+    try calc initial_state expr with Abort n -> (initial_state, n)
 end
diff --git a/src/lib/eval.ml b/src/lib/eval.ml
index 2b7b4b6..c71299e 100644
--- a/src/lib/eval.ml
+++ b/src/lib/eval.ml
@@ -145,7 +145,7 @@ module Make (S : Types.State) (E : Types.Exec) = struct
     let expr = word_cst_to_string word in
     let aexpr = Arith_parser.main Arith_lexer.read (Lexing.from_string expr) in
     let state, i = A.eval ctx.state aexpr in
-    ({ ctx with state }, Ast.Fragment.make (string_of_int i))
+    ({ ctx with state }, i)
 
   (* The minimal amount of context needed between pipeline stages. *)
   type pipeline_ctx = {
@@ -1081,7 +1081,7 @@ module Make (S : Types.State) (E : Types.Exec) = struct
           (Exit.zero ctx, [ [ Fragment.make ~join:`Yes s ] ])
       | Ast.WordArithmeticExpression cst ->
           arithmetic_expansion ctx cst |> fun (ctx, v) ->
-          (Exit.zero ctx, [ [ v ] ])
+          (Exit.zero ctx, [ [ Fragment.make @@ string_of_int v ] ])
       | Ast.WordName s -> (Exit.zero ctx, [ [ Fragment.make s ] ])
       | Ast.WordLiteral s ->
           let v = Fragment.make s in
diff --git a/src/lib/posix/exec.ml b/src/lib/posix/exec.ml
index c5f1ef2..445fe92 100644
--- a/src/lib/posix/exec.ml
+++ b/src/lib/posix/exec.ml
@@ -100,7 +100,6 @@ module Process = struct
           Fiber.fork_daemon ~sw (fun () ->
               Merry.Import.Trace.name "reap-daemon";
               Option.iter Eio.Promise.await delay_reap;
-              Merry.Debug.Log.info (fun f -> f "Delay reap past: %i" t.pid);
               reap t set_exit_status;
               Switch.remove_hook hook;
               `Stop_daemon))
diff --git a/test/docker/Dockerfile.debootstrap b/test/docker/Dockerfile.debootstrap
index 11d1534..6670d43 100644
--- a/test/docker/Dockerfile.debootstrap
+++ b/test/docker/Dockerfile.debootstrap
@@ -1,4 +1,4 @@
-FROM ocaml/opam:debian-13-ocaml-5.3@sha256:3f0e61f92c78a39cd5161d75975809d44fc12fa7e6ae0fbced236aa1a2ae45e9 AS builder
+FROM ocaml/opam:debian-13-ocaml-5.4@sha256:a43344fd8178438c12ce3c78124f966ac44fb015c7cc4ba685f980f9a0460091 AS builder
 
 WORKDIR /home/opam/src