diff --git a/index.js b/index.js
index 14e01e7..a9a7f30 100644
--- a/index.js
+++ b/index.js
@@ -1,4 +1,6 @@
 /**
+ * @typedef {import('nlcst').Root} Root
+ *
  * @typedef {0|1|2|'newline'|'space'|'double-space'|null|undefined} Preferred
  *
  * @typedef Options
@@ -21,13 +23,9 @@ const source = 'retext-sentence-spacing'
  * Plugin to check spacing between sentences.
  * Emit warnings when the spacing does not adhere to the preferred style.
  *
- * @type {import('unified').Plugin<[Options?]>}
+ * @type {import('unified').Plugin<[Options?], Root>}
  */
 export default function retextSentenceSpacing(options = {}) {
-  /**
-   * @typedef {import('unist').Parent} Parent
-   */
-
   let preferred = options.preferred
 
   if (preferred === 'newline') {
@@ -55,7 +53,7 @@ export default function retextSentenceSpacing(options = {}) {
   }
 
   return (tree, file) => {
-    visit(tree, 'ParagraphNode', (/** @type {Parent} */ node) => {
+    visit(tree, 'ParagraphNode', (node) => {
       let index = -1
 
       while (++index < node.children.length) {
diff --git a/package.json b/package.json
index 27bf21d..c47059a 100644
--- a/package.json
+++ b/package.json
@@ -31,6 +31,7 @@
     "index.js"
   ],
   "dependencies": {
+    "@types/nlcst": "^1.0.0",
     "@types/unist": "^2.0.0",
     "nlcst-to-string": "^3.0.0",
     "unified": "^10.0.0",