diff --git a/hosts/ocaml/lib/sx_primitives.ml b/hosts/ocaml/lib/sx_primitives.ml
index e4b9cd2..2b77928 100644
--- a/hosts/ocaml/lib/sx_primitives.ml
+++ b/hosts/ocaml/lib/sx_primitives.ml
@@ -84,10 +84,10 @@ let () =
   register "abs" (fun args ->
     match args with [a] -> Number (Float.abs (as_number a)) | _ -> raise (Eval_error "abs: 1 arg"));
   register "floor" (fun args ->
-    match args with [a] -> Number (Float.of_int (int_of_float (Float.round (as_number a -. 0.5))))
+    match args with [a] -> Number (floor (as_number a))
     | _ -> raise (Eval_error "floor: 1 arg"));
   register "ceil" (fun args ->
-    match args with [a] -> Number (Float.of_int (int_of_float (Float.round (as_number a +. 0.5))))
+    match args with [a] -> Number (ceil (as_number a))
     | _ -> raise (Eval_error "ceil: 1 arg"));
   register "round" (fun args ->
     match args with
@@ -570,6 +570,14 @@ let () =
     match args with [a] -> String (type_of a) | _ -> raise (Eval_error "type-of: 1 arg"));
   register "inspect" (fun args ->
     match args with [a] -> String (inspect a) | _ -> raise (Eval_error "inspect: 1 arg"));
+  register "serialize" (fun args ->
+    match args with
+    | [a] -> String (inspect a)  (* used for dedup keys in compiler *)
+    | _ -> raise (Eval_error "serialize: 1 arg"));
+  register "make-symbol" (fun args ->
+    match args with
+    | [String s] -> Symbol s
+    | _ -> raise (Eval_error "make-symbol: expected string"));
   register "error" (fun args ->
     match args with [String msg] -> raise (Eval_error msg)
     | [a] -> raise (Eval_error (to_string a))
diff --git a/hosts/ocaml/lib/sx_vm.ml b/hosts/ocaml/lib/sx_vm.ml
index 1b04122..6d0cc39 100644
--- a/hosts/ocaml/lib/sx_vm.ml
+++ b/hosts/ocaml/lib/sx_vm.ml
@@ -246,7 +246,12 @@ let rec run vm =
       let args = List.init argc (fun _ -> pop vm) |> List.rev in
       let result =
         try
-          (match Sx_primitives.get_primitive name with
+          (* Check globals first (has env bindings like set-render-active!),
+             then fall back to registered primitives *)
+          let fn_val = try Hashtbl.find vm.globals name with Not_found ->
+            Sx_primitives.get_primitive name
+          in
+          (match fn_val with
            | NativeFn (_, fn) -> fn args
            | _ -> Nil)
         with Eval_error msg ->