diff --git a/src/marpit.js b/src/marpit.js
index 4b91f3a..762962d 100644
--- a/src/marpit.js
+++ b/src/marpit.js
@@ -76,7 +76,7 @@ class Marpit {
    *     container.
    * @param {boolean} [opts.cssNesting=false] Enable CSS nesting support. If
    *     enabled, Marpit will try to make flatten the CSS with nested rules
-   *     before rendering, to make it compatible with Marpit preprocessing.
+   *     before rendering, to make it compatible with Marpit preprocessings.
    * @param {false|number|number[]} [opts.headingDivider=false] Start a new
    *     slide page at before of headings. it would apply to headings whose
    *     larger than or equal to the specified level if a number is given, or
diff --git a/src/theme_set.js b/src/theme_set.js
index 2f8b50b..c5bf69d 100644
--- a/src/theme_set.js
+++ b/src/theme_set.js
@@ -34,6 +34,9 @@ const defaultOptions = {
 class ThemeSet {
   /**
    * Create a ThemeSet instance.
+   *
+   * @param {Object} [opts]
+   * @param {boolean} [opts.cssNesting=true] Enable CSS nesting support.
    */
   constructor(opts = defaultOptions) {
     /**
@@ -90,8 +93,8 @@ class ThemeSet {
     this.metaType = {}
 
     /**
-     * A boolean value indicating whether the theme set should enable CSS
-     * nesting or not.
+     * A boolean value indicating whether the theme set is enabling CSS nesting
+     * or not.
      *
      * @type {boolean}
      */