diff --git a/source b/source
index e16fdfec63c..bf4284c3506 100644
--- a/source
+++ b/source
@@ -97857,10 +97857,10 @@ document.querySelector("button").addEventListener("click", bound);
    <dt>A <dfn for="script" export data-x="concept-script-base-url">base
    URL</dfn></dt>
 
-   <dd><p>A base <span>URL</span> used for <span data-x="resolve a module specifier">resolving
-   module specifiers</span>. This will either be the URL from which the script was obtained, for
-   external scripts, or the <span>document base URL</span> of the containing document, for inline
-   scripts.</p></dd>
+   <dd><p>Null or a base <span>URL</span> used for <span data-x="resolve a module
+   specifier">resolving module specifiers</span>. When non-null, this will either be the URL from
+   which the script was obtained, for external scripts, or the <span>document base URL</span> of the
+   containing document, for inline scripts.</p></dd>
   </dl>