diff --git a/src/index.ts b/src/index.ts
index 8ac5f349..d31ef334 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -56,9 +56,12 @@ const normalizeOptions = async (
   }
   const options: Buildable<NormalizedOptions> = {
     target: 'node14',
-    format: ['cjs'],
     outDir: 'dist',
     ..._options,
+    format:
+      typeof _options.format === 'string'
+        ? [_options.format as Format]
+        : _options.format || ['cjs'],
     dts:
       typeof _options.dts === 'boolean'
         ? _options.dts
diff --git a/src/options.ts b/src/options.ts
index f37320c5..2f793483 100644
--- a/src/options.ts
+++ b/src/options.ts
@@ -72,7 +72,7 @@ export type Options = {
   jsxFragment?: string
   outDir?: string
   outExtension?: OutExtensionFactory
-  format?: Format[]
+  format?: Format[] | string
   globalName?: string
   env?: {
     [k: string]: string
@@ -176,10 +176,11 @@ export type Options = {
 }
 
 export type NormalizedOptions = Omit<
-  MarkRequired<Options, 'entry' | 'format' | 'outDir'>,
-  'dts'
+  MarkRequired<Options, 'entry' | 'outDir'>,
+  'dts' | 'format'
 > & {
   dts?: DtsConfig
   tsconfigResolvePaths: Record<string, string[]>
   tsconfigDecoratorMetadata?: boolean
+  format: Format[]
 }