diff --git a/src/js.rs b/src/js.rs
index c3fa8e62..cff0402c 100644
--- a/src/js.rs
+++ b/src/js.rs
@@ -208,6 +208,20 @@ extern {
     pub fn entries(this: &Array) -> ArrayIterator;
 }
 
+// Number.
+#[wasm_bindgen]
+extern {
+    pub type Number;
+
+    /// The valueOf() method returns the wrapped primitive value of
+    /// a Number object.
+    ///
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/valueOf
+    #[wasm_bindgen(method, js_name = valueOf)]
+    pub fn value_of(this: &Number) -> Number;
+
+}
+
 // Object.
 #[wasm_bindgen]
 extern {
@@ -268,4 +282,4 @@ extern {
     /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/slice
     #[wasm_bindgen(method, js_class = "String")]
     pub fn slice(this: &JsString, start: u32, end: u32) -> JsString;
-}
\ No newline at end of file
+}
diff --git a/tests/all/js_globals/Number.rs b/tests/all/js_globals/Number.rs
new file mode 100644
index 00000000..a78051ea
--- /dev/null
+++ b/tests/all/js_globals/Number.rs
@@ -0,0 +1,32 @@
+#![allow(non_snake_case)]
+
+use super::project;
+
+
+#[test]
+fn value_of() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(proc_macro, wasm_custom_section)]
+
+            extern crate wasm_bindgen;
+            use wasm_bindgen::prelude::*;
+            use wasm_bindgen::js;
+
+            #[wasm_bindgen]
+            pub fn js_value_of(this: &js::Number) -> js::Number {
+                this.value_of()
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                let number = 42;
+                assert.equal(wasm.js_value_of(number), 42);
+                assert.equal(typeof wasm.js_value_of(number), "number");
+            }
+        "#)
+        .test()
+}
diff --git a/tests/all/js_globals/mod.rs b/tests/all/js_globals/mod.rs
index b03c3ae4..25bacbc6 100644
--- a/tests/all/js_globals/mod.rs
+++ b/tests/all/js_globals/mod.rs
@@ -6,6 +6,7 @@ mod Object;
 mod Array;
 mod ArrayIterator;
 mod JsString;
+mod Number;
 
 #[test]
 #[cfg(feature = "std")]