diff --git a/hosts/ocaml/browser/sx_browser.ml b/hosts/ocaml/browser/sx_browser.ml
index 3934ed73..1c1ddb45 100644
--- a/hosts/ocaml/browser/sx_browser.ml
+++ b/hosts/ocaml/browser/sx_browser.ml
@@ -857,13 +857,14 @@ let () =
 
 let () = ignore (env_bind global_env "enable-jit!" (NativeFn ("enable-jit!", fun _ -> _jit_enabled := true; Nil)))
 
-(* Seed _vm_globals with all primitives as NativeFn values.
-   This makes _vm_globals the single source of truth for CALL_PRIM dispatch.
-   OP_DEFINE and registerNative naturally override entries here. *)
+(* Seed BOTH _vm_globals AND global_env with ALL primitives as NativeFn values.
+   Unconditional — native primitives are authoritative for CALL_PRIM dispatch.
+   Must be in both because sync_env_to_vm() copies global_env → _vm_globals. *)
 let () =
   Hashtbl.iter (fun name fn ->
-    if not (Hashtbl.mem _vm_globals name) then
-      Hashtbl.replace _vm_globals name (NativeFn (name, fn))
+    let v = NativeFn (name, fn) in
+    Hashtbl.replace _vm_globals name v;
+    Hashtbl.replace global_env.bindings (intern name) v
   ) Sx_primitives.primitives
 
 (* ================================================================== *)