diff --git a/test/intl402/Collator/unicode-ext-seq-in-private-tag.js b/test/intl402/Collator/unicode-ext-seq-in-private-tag.js
new file mode 100644
index 0000000000..320717d201
--- /dev/null
+++ b/test/intl402/Collator/unicode-ext-seq-in-private-tag.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2017 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-initializecollator
+description: >
+  Unicode extension sequence-like parts are ignored in private-use tags.
+info: |
+  10.1.1 InitializeCollator ( collator, locales, options )
+    ...
+    15. For each element key of relevantExtensionKeys in List order, do
+      a. If key is "co", then
+          i. Let value be r.[[co]].
+         ii. If value is null, let value be "default".
+        iii. Set collator.[[Collation]] to value.
+    ...
+
+  10.3.5 Intl.Collator.prototype.resolvedOptions ()
+    The function returns a new object whose properties and attributes are set as if constructed
+    by an object literal assigning to each of the following properties the value of the
+    corresponding internal slot of this Collator object (see 10.4): ...
+---*/
+
+var c = new Intl.Collator("de-x-u-co-phonebk");
+var resolved = c.resolvedOptions();
+
+assert.sameValue(resolved.collation, "default");
diff --git a/test/intl402/Collator/unicode-ext-seq-with-attribute.js b/test/intl402/Collator/unicode-ext-seq-with-attribute.js
new file mode 100644
index 0000000000..fb4daf257e
--- /dev/null
+++ b/test/intl402/Collator/unicode-ext-seq-with-attribute.js
@@ -0,0 +1,31 @@
+// Copyright (C) 2017 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-initializecollator
+description: >
+  Attributes in Unicode extension subtags should be ignored.
+info: |
+  10.1.1 InitializeCollator ( collator, locales, options )
+    ...
+    15. For each element key of relevantExtensionKeys in List order, do
+      a. If key is "co", then
+          i. Let value be r.[[co]].
+         ii. If value is null, let value be "default".
+        iii. Set collator.[[Collation]] to value.
+    ...
+
+  10.3.5 Intl.Collator.prototype.resolvedOptions ()
+    The function returns a new object whose properties and attributes are set as if constructed
+    by an object literal assigning to each of the following properties the value of the
+    corresponding internal slot of this Collator object (see 10.4): ...
+---*/
+
+var colExpected = new Intl.Collator("de-u-attrval-co-phonebk");
+var colActual = new Intl.Collator("de-u-co-phonebk");
+
+var resolvedExpected = colExpected.resolvedOptions();
+var resolvedActual = colActual.resolvedOptions();
+
+assert.sameValue(resolvedActual.locale, resolvedExpected.locale);
+assert.sameValue(resolvedActual.collation, resolvedExpected.collation);