diff --git a/src/index.js b/src/index.js
index 8a9f367..9033b64 100644
--- a/src/index.js
+++ b/src/index.js
@@ -87,7 +87,7 @@ const { minify: minifyWorker } = require("./minify");
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
  * @param {InferDefaultType<T>} minifyOptions
- * @returns {Promise<MinimizedResult>}
+ * @returns {Promise<MinimizedResult> | MinimizedResult}
  */
 
 /**
diff --git a/src/utils.js b/src/utils.js
index a576746..ccef7d4 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -70,7 +70,7 @@ function throttleAll(limit, tasks) {
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 async function cssnanoMinify(
@@ -192,7 +192,7 @@ cssnanoMinify.supportsWorkerThreads = () => true;
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 async function cssoMinify(input, sourceMap, minimizerOptions) {
@@ -221,7 +221,7 @@ cssoMinify.supportsWorkerThreads = () => true;
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 async function cleanCssMinify(input, sourceMap, minimizerOptions) {
@@ -266,7 +266,7 @@ cleanCssMinify.supportsWorkerThreads = () => true;
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 async function esbuildMinify(input, sourceMap, minimizerOptions) {
@@ -360,7 +360,7 @@ esbuildMinify.supportsWorkerThreads = () => false;
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 async function parcelCssMinify(input, sourceMap, minimizerOptions) {
@@ -406,7 +406,7 @@ parcelCssMinify.supportsWorkerThreads = () => false;
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 async function lightningCssMinify(input, sourceMap, minimizerOptions) {
@@ -452,7 +452,7 @@ lightningCssMinify.supportsWorkerThreads = () => false;
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 async function swcMinify(input, sourceMap, minimizerOptions) {
diff --git a/test/minify-option.test.js b/test/minify-option.test.js
index 6e26c88..855cda9 100644
--- a/test/minify-option.test.js
+++ b/test/minify-option.test.js
@@ -152,7 +152,7 @@ describe('"minify" option', () => {
         { test: ".three{background: white;}" },
       ],
       minify: [
-        async (data, inputMap, minimizerOptions) => {
+        (data, inputMap, minimizerOptions) => {
           const [input] = Object.values(data);
           return {
             code: `${input}\n.one{color: red;}\n${minimizerOptions.test}\n`,
diff --git a/types/index.d.ts b/types/index.d.ts
index 8ff1703..43431b2 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -179,7 +179,7 @@ type BasicMinimizerImplementation<T> = (
   input: Input,
   sourceMap: RawSourceMap | undefined,
   minifyOptions: InferDefaultType<T>,
-) => Promise<MinimizedResult>;
+) => Promise<MinimizedResult> | MinimizedResult;
 type MinimizeFunctionHelpers = {
   supportsWorkerThreads?: (() => boolean | undefined) | undefined;
 };
diff --git a/types/utils.d.ts b/types/utils.d.ts
index 9549d12..7d9615d 100644
--- a/types/utils.d.ts
+++ b/types/utils.d.ts
@@ -26,13 +26,13 @@ export function memoize<T>(fn: (() => any) | undefined): () => T;
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 export function cssnanoMinify(
   input: Input,
   sourceMap: RawSourceMap | undefined,
-  minimizerOptions?: CustomOptions,
+  minimizerOptions?: import("./index.js").CustomOptions | undefined,
 ): Promise<MinimizedResult>;
 export namespace cssnanoMinify {
   function supportsWorkerThreads(): boolean;
@@ -40,13 +40,13 @@ export namespace cssnanoMinify {
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 export function cssoMinify(
   input: Input,
   sourceMap: RawSourceMap | undefined,
-  minimizerOptions: CustomOptions,
+  minimizerOptions?: import("./index.js").CustomOptions | undefined,
 ): Promise<MinimizedResult>;
 export namespace cssoMinify {
   function supportsWorkerThreads(): boolean;
@@ -54,13 +54,13 @@ export namespace cssoMinify {
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 export function cleanCssMinify(
   input: Input,
   sourceMap: RawSourceMap | undefined,
-  minimizerOptions: CustomOptions,
+  minimizerOptions?: import("./index.js").CustomOptions | undefined,
 ): Promise<MinimizedResult>;
 export namespace cleanCssMinify {
   function supportsWorkerThreads(): boolean;
@@ -68,13 +68,13 @@ export namespace cleanCssMinify {
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 export function esbuildMinify(
   input: Input,
   sourceMap: RawSourceMap | undefined,
-  minimizerOptions: CustomOptions,
+  minimizerOptions?: import("./index.js").CustomOptions | undefined,
 ): Promise<MinimizedResult>;
 export namespace esbuildMinify {
   function supportsWorkerThreads(): boolean;
@@ -82,13 +82,13 @@ export namespace esbuildMinify {
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 export function parcelCssMinify(
   input: Input,
   sourceMap: RawSourceMap | undefined,
-  minimizerOptions: CustomOptions,
+  minimizerOptions?: import("./index.js").CustomOptions | undefined,
 ): Promise<MinimizedResult>;
 export namespace parcelCssMinify {
   function supportsWorkerThreads(): boolean;
@@ -96,13 +96,13 @@ export namespace parcelCssMinify {
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 export function lightningCssMinify(
   input: Input,
   sourceMap: RawSourceMap | undefined,
-  minimizerOptions: CustomOptions,
+  minimizerOptions?: import("./index.js").CustomOptions | undefined,
 ): Promise<MinimizedResult>;
 export namespace lightningCssMinify {
   function supportsWorkerThreads(): boolean;
@@ -110,13 +110,13 @@ export namespace lightningCssMinify {
 /**
  * @param {Input} input
  * @param {RawSourceMap | undefined} sourceMap
- * @param {CustomOptions} minimizerOptions
+ * @param {CustomOptions} [minimizerOptions]
  * @return {Promise<MinimizedResult>}
  */
 export function swcMinify(
   input: Input,
   sourceMap: RawSourceMap | undefined,
-  minimizerOptions: CustomOptions,
+  minimizerOptions?: import("./index.js").CustomOptions | undefined,
 ): Promise<MinimizedResult>;
 export namespace swcMinify {
   function supportsWorkerThreads(): boolean;