diff --git a/hosts/ocaml/lib/sx_vm.ml b/hosts/ocaml/lib/sx_vm.ml
index c9b32647..ef0344af 100644
--- a/hosts/ocaml/lib/sx_vm.ml
+++ b/hosts/ocaml/lib/sx_vm.ml
@@ -582,10 +582,30 @@ let jit_compile_lambda (l : lambda) globals =
       | _ ->
         (* Compiler loaded from source — call through CEK *)
         Sx_ref.eval_expr (List [compile_fn; quoted]) (Env (make_env ())) in
-    (* Don't inject closure bindings into globals — GLOBAL_GET falls through
-       to vm_closure_env which has LIVE bindings. Injecting creates stale
-       snapshots that break mutable closure variables (set! on pos, etc.). *)
-    let effective_globals = globals in
+    (* Inject closure bindings into globals so GLOBAL_GET can find them.
+       Only injects values not already present in globals (preserves
+       existing defines). Mutable closure vars get stale snapshots here
+       but GLOBAL_SET writes back to vm_closure_env, and GLOBAL_GET
+       falls through to vm_closure_env if the global is stale. *)
+    let effective_globals =
+      let closure = l.l_closure in
+      let count = ref 0 in
+      let rec inject env =
+        Hashtbl.iter (fun id v ->
+          let name = Sx_types.unintern id in
+          if not (Hashtbl.mem globals name) then begin
+            Hashtbl.replace globals name v;
+            incr count
+          end
+        ) env.bindings;
+        match env.parent with Some p -> inject p | None -> ()
+      in
+      if Hashtbl.length closure.bindings > 0 || closure.parent <> None then
+        inject closure;
+      if !count > 0 then
+        Printf.eprintf "[jit] %s: injected %d closure bindings\n%!" fn_name !count;
+      globals
+    in
     (match result with
     | Dict d when Hashtbl.mem d "bytecode" ->
       let outer_code = code_from_value result in