diff --git a/lib/js/runtime.sx b/lib/js/runtime.sx
index b50bac9d..3489f095 100644
--- a/lib/js/runtime.sx
+++ b/lib/js/runtime.sx
@@ -1618,7 +1618,7 @@
 
 (define js-global-is-nan (fn (v) (js-number-is-nan (js-to-number v))))
 
-(define Number {:isFinite js-number-is-finite :MAX_SAFE_INTEGER 9007199254740991 :EPSILON 2.22045e-16 :MAX_VALUE 0 :POSITIVE_INFINITY inf :__callable__ js-to-number :isInteger js-number-is-integer :isNaN js-number-is-nan :isSafeInteger js-number-is-safe-integer :NEGATIVE_INFINITY -inf :NaN 0 :MIN_VALUE 4.94066e-324 :MIN_SAFE_INTEGER -9007199254740991})
+(define Number {:isFinite js-number-is-finite :MAX_SAFE_INTEGER 9007199254740991 :EPSILON 2.22045e-16 :MAX_VALUE 0 :POSITIVE_INFINITY inf :__callable__ js-to-number :isInteger js-number-is-integer :prototype {:valueOf (fn () (js-this)) :toString (fn (&rest args) (js-to-string (js-this))) :toFixed (fn (d) (js-to-string (js-this)))} :isNaN js-number-is-nan :isSafeInteger js-number-is-safe-integer :NEGATIVE_INFINITY -inf :NaN 0 :MIN_VALUE 4.94066e-324 :MIN_SAFE_INTEGER -9007199254740991})
 
 (define isFinite js-global-is-finite)