diff --git a/storage/storage.rkt b/storage/storage.rkt
index c273a1e..c5eb51c 100644
--- a/storage/storage.rkt
+++ b/storage/storage.rkt
@@ -20,20 +20,30 @@
   (inexact->exact (js-number->number (get-attr localStorage "length"))))
 
 (define (storage-key i)
+  (unless (exact-nonnegative-integer? i)
+    (raise-type-error 'storage-key "natural" i))
   (js-string->string (call-method localStorage "key" (number->js-number i))))
 
 (define (storage-ref name)
+  (unless (string? name)
+    (raise-type-error 'storage-ref "string" name))
   (define val (call-method localStorage "getItem" (string->js-string name)))
   (if (js-null? val)
       #f
       (js-string->string val)))
 
 (define (storage-set! name value)
+  (unless (string? name)
+    (raise-type-error 'storage-set! "string" name 0))
+  (unless (string? value)
+    (raise-type-error 'storage-set! "string" value 1))
   (void (call-method localStorage "setItem"
                      (string->js-string name)
                      (string->js-string value))))
 
 (define (storage-remove! name)
+  (unless (string? name)
+    (raise-type-error 'storage-remove! "string" name))
   (void (call-method localStorage "removeItem"
                      (string->js-string name))))