diff --git a/src/js.rs b/src/js.rs
index e50b3b40..cc39d01e 100644
--- a/src/js.rs
+++ b/src/js.rs
@@ -241,6 +241,15 @@ extern {
     /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/abs
     #[wasm_bindgen(static_method_of = Math)]
     pub fn abs(number: i32) -> Number;
+
+    /// The Math.acos() function returns the arccosine (in radians) of a
+    /// number, that is ∀x∊[-1;1]
+    /// Math.acos(x) = arccos(x) = the unique y∊[0;π] such that cos(y)=x
+    ///
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/acos
+    #[wasm_bindgen(static_method_of = Math)]
+    pub fn acos(adjacent: i32, hypotenuse: i32) -> Number;
+
 }
 
 // Number.
diff --git a/tests/all/js_globals/Math.rs b/tests/all/js_globals/Math.rs
index 98992f45..beee88bb 100644
--- a/tests/all/js_globals/Math.rs
+++ b/tests/all/js_globals/Math.rs
@@ -24,7 +24,33 @@ fn abs() {
 
             export function test() {
                 assert.equal(wasm.abs(-32), Math.abs(-32));
-                assert.equal(wasm.abs(32), 32));
+                assert.equal(wasm.abs(32), 32);
+            }
+        "#)
+        .test()
+}
+
+#[test]
+fn acos() {
+    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 acos(adjacent: i32, hypotenuse: i32) -> js::Number {
+                js::Math::acos(adjacent, hypotenuse)
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                assert.equal(wasm.acos(-1, 1), Math.PI);
             }
         "#)
         .test()