diff --git a/js/src/tests/jstests.list b/js/src/tests/jstests.list
index 8952a819b72e..eaca963884e5 100644
--- a/js/src/tests/jstests.list
+++ b/js/src/tests/jstests.list
@@ -49,6 +49,9 @@ skip-if(!this.hasOwnProperty("SharedArrayBuffer")) script test262/built-ins/Arra
 skip-if(!this.hasOwnProperty("SharedArrayBuffer")) script test262/built-ins/ArrayBuffer/prototype/slice/this-is-sharedarraybuffer.js
 skip-if(!this.hasOwnProperty("SharedArrayBuffer")) script test262/built-ins/TypedArrays/internals/Get/indexed-value-sab.js
 
+# flatMap and flatten are Nightly-only
+skip-if(!Array.prototype.flatMap) include test262/built-ins/Array/prototype/flatMap/jstests.list
+skip-if(!Array.prototype.flatten) include test262/built-ins/Array/prototype/flatten/jstests.list
 
 #####################################
 # Test262 tests disabled on browser #
diff --git a/js/src/tests/test262-update.py b/js/src/tests/test262-update.py
index f1033daad265..f47ced6a885f 100755
--- a/js/src/tests/test262-update.py
+++ b/js/src/tests/test262-update.py
@@ -20,8 +20,6 @@ from itertools import chain, imap
 # Skip all tests which use features not supported in SpiderMonkey.
 UNSUPPORTED_FEATURES = set([
                             "tail-call-optimization",
-                            "Array.prototype.flatMap",
-                            "Array.prototype.flatten",
                             "BigInt",
                             "class-fields-public",
                             "class-fields-private",
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatMap/array-like-objects.js b/js/src/tests/test262/built-ins/Array/prototype/flatMap/array-like-objects.js
index 9555179c15aa..e530d3d8f9f6 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatMap/array-like-objects.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatMap/array-like-objects.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatMap is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatMap/bound-function-argument.js b/js/src/tests/test262/built-ins/Array/prototype/flatMap/bound-function-argument.js
index 5cfa9a7486b3..165d111a108f 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatMap/bound-function-argument.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatMap/bound-function-argument.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatMap is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatMap/depth-always-one.js b/js/src/tests/test262/built-ins/Array/prototype/flatMap/depth-always-one.js
index a4930e0c831d..1eea96006c56 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatMap/depth-always-one.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatMap/depth-always-one.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatMap is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatMap/length.js b/js/src/tests/test262/built-ins/Array/prototype/flatMap/length.js
index d3023c78e4ab..36925584ac48 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatMap/length.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatMap/length.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatMap is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatMap/name.js b/js/src/tests/test262/built-ins/Array/prototype/flatMap/name.js
index 24316e00cbfb..25e50956054e 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatMap/name.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatMap/name.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatMap is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatMap/non-callable-argument-throws.js b/js/src/tests/test262/built-ins/Array/prototype/flatMap/non-callable-argument-throws.js
index e3441db7e666..eee434dc889e 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatMap/non-callable-argument-throws.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatMap/non-callable-argument-throws.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatMap is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatMap/non-object-ctor-throws.js b/js/src/tests/test262/built-ins/Array/prototype/flatMap/non-object-ctor-throws.js
index e4add0ad703e..3bc334661f97 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatMap/non-object-ctor-throws.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatMap/non-object-ctor-throws.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatMap is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatMap/null-undefined-input-throws.js b/js/src/tests/test262/built-ins/Array/prototype/flatMap/null-undefined-input-throws.js
index 99070a9a6f39..4e78aead19a8 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatMap/null-undefined-input-throws.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatMap/null-undefined-input-throws.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatMap is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatMap/thisArg-argument-strict.js b/js/src/tests/test262/built-ins/Array/prototype/flatMap/thisArg-argument-strict.js
index 91c17ec2e673..8462a0218301 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatMap/thisArg-argument-strict.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatMap/thisArg-argument-strict.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatMap is not supported
 'use strict';
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/array-like-objects.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/array-like-objects.js
index 857ac3838d90..2d0aa4efba4c 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/array-like-objects.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/array-like-objects.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/bound-function-call.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/bound-function-call.js
index 7c048c926215..90ee25470bbe 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/bound-function-call.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/bound-function-call.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/empty-array-elements.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/empty-array-elements.js
index 1995688c77ef..4bff8e1ac367 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/empty-array-elements.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/empty-array-elements.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/empty-object-elements.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/empty-object-elements.js
index 7060879c5844..cedf54a0836f 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/empty-object-elements.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/empty-object-elements.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/length.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/length.js
index 81a9f198c161..e3a5b87cf7d7 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/length.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/length.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/name.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/name.js
index 5bfd94c4ceb4..313695819881 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/name.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/name.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/non-numeric-depth-should-not-throw.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/non-numeric-depth-should-not-throw.js
index 4ac3ea7d8b25..505d5f98f64d 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/non-numeric-depth-should-not-throw.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/non-numeric-depth-should-not-throw.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/non-object-ctor-throws.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/non-object-ctor-throws.js
index b01c4ef974f9..05a44774a26e 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/non-object-ctor-throws.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/non-object-ctor-throws.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/null-undefined-elements.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/null-undefined-elements.js
index fd10b8654687..ce9b3a4bdf57 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/null-undefined-elements.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/null-undefined-elements.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/null-undefined-input-throws.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/null-undefined-input-throws.js
index 47a94bf4f44c..f5dc8fde27f6 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/null-undefined-input-throws.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/null-undefined-input-throws.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/positive-infinity.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/positive-infinity.js
index a76bd519a72a..5b350370e84f 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/positive-infinity.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/positive-infinity.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/prop-desc.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/prop-desc.js
index b5120988fcbb..b4e87e55a361 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/prop-desc.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/prop-desc.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
diff --git a/js/src/tests/test262/built-ins/Array/prototype/flatten/symbol-object-create-null-depth-throws.js b/js/src/tests/test262/built-ins/Array/prototype/flatten/symbol-object-create-null-depth-throws.js
index c99d709a8938..135bfb4af34c 100644
--- a/js/src/tests/test262/built-ins/Array/prototype/flatten/symbol-object-create-null-depth-throws.js
+++ b/js/src/tests/test262/built-ins/Array/prototype/flatten/symbol-object-create-null-depth-throws.js
@@ -1,4 +1,3 @@
-// |reftest| skip -- Array.prototype.flatten is not supported
 // Copyright (C) 2018 Shilpi Jain and Michael Ficarra. All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 /*---