diff --git a/apps/generator/docs/api.md b/apps/generator/docs/api.md
index 42d7309e5..3dd56e79e 100644
--- a/apps/generator/docs/api.md
+++ b/apps/generator/docs/api.md
@@ -39,9 +39,9 @@ Reference API documentation for AsyncAPI Generator library.
         * [.executeAfterHook()](#Generator+executeAfterHook) ⇒ `Promise.<void>`
         * [.parseInput()](#Generator+parseInput)
         * [.configureTemplate()](#Generator+configureTemplate)
-        * ~~[.generateFromString(asyncapiString, [parseOptions])](#Generator+generateFromString) ⇒ `Promise`~~
-        * [.generateFromURL(asyncapiURL)](#Generator+generateFromURL) ⇒ `Promise`
-        * [.generateFromFile(asyncapiFile)](#Generator+generateFromFile) ⇒ `Promise`
+        * ~~[.generateFromString(asyncapiString, [parseOptions])](#Generator+generateFromString) ⇒ `Promise.<(TemplateRenderResult|undefined)>`~~
+        * [.generateFromURL(asyncapiURL)](#Generator+generateFromURL) ⇒ `Promise.<(TemplateRenderResult|undefined)>`
+        * [.generateFromFile(asyncapiFile)](#Generator+generateFromFile) ⇒ `Promise.<(TemplateRenderResult|undefined)>`
         * [.installTemplate([force])](#Generator+installTemplate)
     * _static_
         * [.getTemplateFile(templateName, filePath, [templatesDir])](#Generator.getTemplateFile) ⇒ `Promise`
diff --git a/apps/generator/lib/generator.js b/apps/generator/lib/generator.js
index 077634e1c..2414cc6a7 100644
--- a/apps/generator/lib/generator.js
+++ b/apps/generator/lib/generator.js
@@ -436,7 +436,7 @@ class Generator {
    * @param  {String} asyncapiString AsyncAPI string to use as source.
    * @param  {Object} [parseOptions={}] AsyncAPI Parser parse options. Check out {@link https://www.github.com/asyncapi/parser-js|@asyncapi/parser} for more information.
    * @deprecated Use the `generate` function instead. Just change the function name and it works out of the box.
-   * @return {Promise}
+   * @return {Promise<TemplateRenderResult|undefined>}
    */
   async generateFromString(asyncapiString, parseOptions = {}) {
     const isParsableCompatible = asyncapiString && typeof asyncapiString === 'string';
@@ -466,7 +466,7 @@ class Generator {
    * }
    *
    * @param  {String} asyncapiURL Link to AsyncAPI file
-   * @return {Promise}
+   * @return {Promise<TemplateRenderResult|undefined>}
    */
   async generateFromURL(asyncapiURL) {
     const doc = await fetchSpec(asyncapiURL);
@@ -493,7 +493,7 @@ class Generator {
    * }
    *
    * @param  {String} asyncapiFile AsyncAPI file to use as source.
-   * @return {Promise}
+   * @return {Promise<TemplateRenderResult|undefined>}
    */
   async generateFromFile(asyncapiFile) {
     const doc = await readFile(asyncapiFile, { encoding: 'utf8' });