diff --git a/spec/collator.html b/spec/collator.html
index 57dac1d3..c1e6d562 100644
--- a/spec/collator.html
+++ b/spec/collator.html
@@ -14,6 +14,10 @@ <h1>InitializeCollator ( _collator_, _locales_, _options_ )</h1>
         The abstract operation InitializeCollator accepts the arguments _collator_ (which must be an object), _locales_, and _options_. It initializes _collator_ as a *Collator* object. The following steps are taken:
       </p>
 
+      <p>
+        The following algorithm refers to the `type` nonterminal from <a href="https://www.unicode.org/reports/tr35/#Unicode_locale_identifier">UTS 35's Unicode Locale Identifier grammar</a>.
+      </p>
+      
       <emu-alg>
         1. Let _requestedLocales_ be ? CanonicalizeLocaleList(_locales_).
         1. If _options_ is *undefined*, then
@@ -29,6 +33,10 @@ <h1>InitializeCollator ( _collator_, _locales_, _options_ )</h1>
         1. Let _opt_ be a new Record.
         1. Let _matcher_ be ? GetOption(_options_, *"localeMatcher"*, *"string"*, &laquo; *"lookup"*, *"best fit"* &raquo;, *"best fit"*).
         1. Set _opt_.[[localeMatcher]] to _matcher_.
+        1. Let _collation_ be ? GetOption(_options_, *"collation"*, *"string"*, *undefined*, *undefined*).
+        1. If _collation_ is not *undefined*, then
+          1. If _collation_ does not match the Unicode Locale Identifier `type` nonterminal, throw a *RangeError* exception.
+        1. Set _opt_.[[co]] to _collation_.
         1. Let _numeric_ be ? GetOption(_options_, *"numeric"*, *"boolean"*, *undefined*, *undefined*).
         1. If _numeric_ is not *undefined*, then
           1. Let _numeric_ be ! ToString(_numeric_).