diff --git a/lib/encryptionUtils.js b/lib/encryptionUtils.js
index 916ef17a5c..f0c46dee71 100644
--- a/lib/encryptionUtils.js
+++ b/lib/encryptionUtils.js
@@ -19,7 +19,7 @@ const SchemaString = require('./schema/string');
  *
  * @param {import('.').Schema} schema
  * @param {string} path
- * @returns
+ * @returns {string}
  */
 function inferBSONType(schema, path) {
   const type = schema.path(path);