diff --git a/compiler/compiler-helper.rkt b/compiler/compiler-helper.rkt
new file mode 100644
index 0000000..e5e89c0
--- /dev/null
+++ b/compiler/compiler-helper.rkt
@@ -0,0 +1,38 @@
+#lang racket/base
+
+(provide ensure-const-value)
+
+(define (ensure-const-value x)
+  (cond
+   [(symbol? x)
+    x]
+   [(boolean? x)
+    x]
+   [(string? x)
+    x]
+   [(number? x)
+    x]
+   [(void? x)
+    x]
+   [(null? x)
+    x]
+   [(char? x)
+    x]
+   [(bytes? x)
+    x]
+   [(path? x)
+    x]
+   [(pair? x)
+    (begin (ensure-const-value (car x))
+           (ensure-const-value (cdr x))
+           x)]
+   [(vector? x)
+    (begin (for-each ensure-const-value (vector->list x)))
+    x]
+   [(box? x)
+    (ensure-const-value (unbox x))
+    x]
+   [else
+    (error 'ensure-const-value "Not a const value: ~s\n" x)]))
+         
+    
\ No newline at end of file
diff --git a/compiler/compiler.rkt b/compiler/compiler.rkt
index d77f236..72871b4 100644
--- a/compiler/compiler.rkt
+++ b/compiler/compiler.rkt
@@ -13,9 +13,13 @@
          racket/bool
          racket/list
          racket/match)
+
 (require/typed "../logger.rkt"
                [log-debug (String -> Void)])
 
+(require/typed "compiler-helper.rkt"
+               [ensure-const-value (Any -> const-value)])
+
 (provide (rename-out [-compile compile])
          compile-general-procedure-call
          append-instruction-sequences)
@@ -450,7 +454,8 @@
     (end-with-linkage linkage
                       cenv
                       (append-instruction-sequences
-                       (make-AssignImmediateStatement target (make-Const (Constant-v exp)))
+                       (make-AssignImmediateStatement target (make-Const
+                                                              (ensure-const-value (Constant-v exp))))
                        singular-context-check))))
 
 
@@ -1208,7 +1213,7 @@
   (map (lambda: ([e : Expression])
          (cond
            [(Constant? e)
-            (make-Const (Constant-v e))]
+            (make-Const (ensure-const-value (Constant-v e)))]
            [(LocalRef? e)
             (make-EnvLexicalReference (LocalRef-depth e)
                                       (LocalRef-unbox? e))]
@@ -1655,7 +1660,7 @@
           '?]))]
     
     [(Constant? exp)
-     (make-Const (Constant-v exp))]
+     (make-Const (ensure-const-value (Constant-v exp)))]
     
     [(PrimitiveKernelValue? exp)
      exp]
diff --git a/compiler/il-structs.rkt b/compiler/il-structs.rkt
index 5af500f..853a964 100644
--- a/compiler/il-structs.rkt
+++ b/compiler/il-structs.rkt
@@ -64,12 +64,27 @@
   #:transparent)
 
 
+(define-type const-value
+  (Rec C
+       (U Symbol
+          String
+          Number
+          Boolean
+          Void
+          Null
+          Char
+          Bytes
+          Path
+          (Pairof C C)
+          (Vectorof C)
+          (Boxof C))))
+
 
 (define-struct: Label ([name : Symbol])
   #:transparent)
 (define-struct: Reg ([name : AtomicRegisterSymbol])
   #:transparent)
-(define-struct: Const ([const : Any])
+(define-struct: Const ([const : const-value])
   #:transparent)
 
 ;; Limited arithmetic on OpArgs
diff --git a/js-assembler/assemble-helpers.rkt b/js-assembler/assemble-helpers.rkt
index e98b8ee..cef6ec9 100644
--- a/js-assembler/assemble-helpers.rkt
+++ b/js-assembler/assemble-helpers.rkt
@@ -109,7 +109,7 @@
 ;; fixme: use js->string
 (: assemble-const (Const -> String))
 (define (assemble-const stmt)
-  (let: loop : String ([val : Any (Const-const stmt)])
+  (let: loop : String ([val : const-value (Const-const stmt)])
         (cond [(symbol? val)
                (format "RUNTIME.makeSymbol(~s)" (symbol->string val))]
               [(pair? val)
@@ -136,13 +136,15 @@
               [(path? val)
                (format "RUNTIME.makePath(~s)"
                        (path->string val))]
-              #;[(vector? val)
+              [(vector? val)
                (format "RUNTIME.makeVector(~s)"
                        (string-join (for/list ([elt (vector->list val)])
                                         (loop elt))
                                     ","))]
-              [else
-               (error 'assemble-const "Unsupported datum ~s" val)])))
+              [(box? val)
+               (format "RUNTIME.makeBox(~s)"
+                       (loop (unbox val)))])))
+
 
 
 (: assemble-listof-assembled-values ((Listof String) -> String))