diff --git a/document/js-api/index.bs b/document/js-api/index.bs
index 0c82236a18..644d920e07 100644
--- a/document/js-api/index.bs
+++ b/document/js-api/index.bs
@@ -720,10 +720,10 @@ dictionary GlobalDescriptor {
   boolean mutable = false;
 };
 
-[LegacyNamespace=WebAssembly, Constructor(GlobalDescriptor descriptor, unrestricted double value = 0), Exposed=(Window,Worker,Worklet)]
+[LegacyNamespace=WebAssembly, Constructor(GlobalDescriptor descriptor, optional any value), Exposed=(Window,Worker,Worklet)]
 interface Global {
-  unrestricted double valueOf();
-  attribute unrestricted double value;
+  any valueOf();
+  attribute any value;
 };
 </pre>
 
@@ -753,11 +753,19 @@ which can be simultaneously referenced by multiple {{Instance}} objects. Each
     1. Otherwise, throw a {{TypeError}} exception.
 </div>
 
+<div algorithm>
+    The algorithm <dfn>DefaultValue</dfn>(|valuetype|) performs the following steps:
+    1. If |valuetype| equals [=𝗂𝟥𝟤=], return [=𝗂𝟥𝟤.𝖼𝗈𝗇𝗌𝗍=] 0.
+    1. If |valuetype| equals [=𝖿𝟥𝟤=], return [=𝖿𝟥𝟤.𝖼𝗈𝗇𝗌𝗍=] 0.
+    1. If |valuetype| equals [=𝖿𝟨𝟦=], return [=𝖿𝟨𝟦.𝖼𝗈𝗇𝗌𝗍=] 0.
+    1. Otherwise, throw a {{TypeError}} exception.
+</div>
+
 <div algorithm>
     The <dfn constructor for="Global">Global(descriptor, v)</dfn> constructor, when invoked, performs the following steps:
     1. Let |mutable| be |descriptor|["mutable"].
     1. Let |valuetype| be [=ToValueType=](|descriptor|["value"]).
-    1. Let |value| be [=ToWebAssemblyValue=](|v|, |valuetype|).
+    1. If |v| is undefined, let |value| be [=DefaultValue=](|valuetype|); otherwise, let |value| be [=ToWebAssemblyValue=](|v|, |valuetype|).
     1. If |mutable| is true, let |globaltype| be [=var=] |valuetype|; otherwise, let |globaltype| be [=const=] |valuetype|.
     1. Let |store| be the current agent's [=associated store=].
     1. Let (|store|, |globaladdr|) be [=alloc_global=](|store|, |globaltype|, |value|). <!-- TODO(littledan): Report allocation failure https://github.com/WebAssembly/spec/issues/584 -->