diff --git a/README.md b/README.md
index 3effee8..768b7df 100644
--- a/README.md
+++ b/README.md
@@ -23,16 +23,17 @@ Insert script to `package.json`
 ```
 
 ## CLI
-| Flag              | Description                           | Default                    |            
-|-------------------|---------------------------------------|----------------------------|
-| `--help`          | Display usage hints                   |                            |
-| `--cwd`           | Set current working dir               | `process.cwd()`            |  
-| `--entry`         | Define pkg entry point                | `./index.ts`               |   
-| `--tsconfig`      | Define path(s) to project's TS config |                            |
-| `--customTypings` | Attach custom libdefs to d.ts bundle  |                            |
-| `--cache`         | Dir for temporary assets              | `tempy.directory()`        |
-| `--dtsOut`        | **TS** typings output                 | `typings/index.d.ts`       |
-| `--flowOut`       | **Flow** libdef output                | `flow-typed/index.flow.js` |
+| Flag              | Description                                                 | Default                    |            
+|-------------------|-------------------------------------------------------------|----------------------------|
+| `--help`          | Display usage hints                                         |                            |
+| `--cwd`           | Set current working dir                                     | `process.cwd()`            |  
+| `--entry`         | Define pkg entry point                                      | `./index.ts`               |
+| `--ext`           | Extension to use in module declarations. `''` to unset any. | `.js`                      |        
+| `--tsconfig`      | Define path(s) to project's TS config                       |                            |
+| `--customTypings` | Attach custom libdefs to d.ts bundle                        |                            |
+| `--cache`         | Dir for temporary assets                                    | `tempy.directory()`        |
+| `--dtsOut`        | **TS** typings output                                       | `typings/index.d.ts`       |
+| `--flowOut`       | **Flow** libdef output                                      | `flow-typed/index.flow.js` |
 
 ## License
 [MIT](./LICENSE)
diff --git a/src/main/ts/cli.ts b/src/main/ts/cli.ts
index ea3d2c0..cc15505 100644
--- a/src/main/ts/cli.ts
+++ b/src/main/ts/cli.ts
@@ -11,7 +11,8 @@ const cli = meow(
       --cwd, working dir path
       --tsconfig
       --customTypings, attach custom libdefs to d.ts bundle
-      --entry, alias entry (<pkgName>/target/es5/index by default)
+      --entry, pkg entry point (<pkgName>/index by default)
+      --ext, extension to use in module declarations (default: .js)
       --dtsOut, dts output (typings/index.d.ts by default)
       --flowOut, flow output (flow-typed/index.flow.js by default)
 `,
@@ -38,6 +39,12 @@ const cli = meow(
       cache: {
         type: 'string',
       },
+      entry: {
+        type: 'string',
+      },
+      ext: {
+        type: 'string',
+      },
     },
   },
 )
diff --git a/src/main/ts/dts.ts b/src/main/ts/dts.ts
index 747042c..24c0e97 100644
--- a/src/main/ts/dts.ts
+++ b/src/main/ts/dts.ts
@@ -14,6 +14,7 @@ export const generate = (
   name: string,
   cwd: string,
   entryPoints: Record<string, string> = {},
+  ext: string,
 ): string => {
   const cfg = populateSync(fse.readJsonSync(tsconfig), {
     merge: {
@@ -40,7 +41,7 @@ export const generate = (
     outDir,
     entryPoints,
     conceal: false,
-    ext: '.js',
+    ext,
     cwd
   })['bundle.d.ts']
 }
@@ -55,6 +56,7 @@ export const pipe: IExecPipe = (ctx): IContext => {
   const {
     name,
     entry,
+    ext,
     tsconfig = [],
     customTypings = [],
     dtsOut,
@@ -66,7 +68,8 @@ export const pipe: IExecPipe = (ctx): IContext => {
       cfg,
       name,
       cwd,
-      i === 0 ? {'.': entry ?? './index.ts'} : {}
+      i === 0 ? {'.': entry ?? './index.ts'} : {},
+      ext
     ),
   ).join('\n\n')
 
diff --git a/src/main/ts/interface.ts b/src/main/ts/interface.ts
index 77a3d05..3631976 100644
--- a/src/main/ts/interface.ts
+++ b/src/main/ts/interface.ts
@@ -15,6 +15,7 @@ export type ICmdInvokeOptions = {
 export type ICliFlags = {
   cwd?: string
   entry?: string
+  ext?: string
   dtsOut?: string
   flowOut?: string
   tsconfig?: string[]
@@ -27,6 +28,7 @@ export type IContext = ICliFlags & {
   cwd: string
   name: string
   entry: string
+  ext: string
   dtsOut: string
   flowOut: string
 } & TFlags
diff --git a/src/main/ts/libdefkit.ts b/src/main/ts/libdefkit.ts
index 8087f73..0eae313 100644
--- a/src/main/ts/libdefkit.ts
+++ b/src/main/ts/libdefkit.ts
@@ -16,6 +16,7 @@ export const normalize: IExecPipe = (flags: ICliFlags): IContext => {
   const temp = temporaryDirectory()
   const name = fs.readJsonSync(join(cwd, 'package.json')).name
   const entry = flags.entry ?? `./index.ts`
+  const ext = flags.ext ?? '.js'
   const dtsOut = flags.dtsOut === 'false'
     ? join(temp, 'index.d.ts')
     : flags.dtsOut ?? join(cwd, 'typings', 'index.d.ts')
@@ -23,7 +24,7 @@ export const normalize: IExecPipe = (flags: ICliFlags): IContext => {
     ? join(temp, 'index.flow.js')
     : flags.flowOut ?? join(cwd, 'flow-typed', 'index.flow.js')
 
-  return { cache, ...flags, cwd, name, entry, dtsOut, flowOut }
+  return { cache, ...flags, cwd, name, entry, ext, dtsOut, flowOut }
 }
 
 export const clear: IExecPipe = (ctx) => {
diff --git a/src/test/ts/libdefkit.ts.snap b/src/test/ts/libdefkit.ts.snap
index 4c20a99..1c5d424 100644
--- a/src/test/ts/libdefkit.ts.snap
+++ b/src/test/ts/libdefkit.ts.snap
@@ -23,6 +23,7 @@ declare module "@qiwi/libdefkit/target/es6/interface.js" {
     export type ICliFlags = {
         cwd?: string;
         entry?: string;
+        ext?: string;
         dtsOut?: string;
         flowOut?: string;
         tsconfig?: string[];
@@ -34,6 +35,7 @@ declare module "@qiwi/libdefkit/target/es6/interface.js" {
         cwd: string;
         name: string;
         entry: string;
+        ext: string;
         dtsOut: string;
         flowOut: string;
     } & TFlags;
@@ -57,7 +59,7 @@ declare module "@qiwi/libdefkit/target/es6/util.js" {
 }
 declare module "@qiwi/libdefkit/target/es6/dts.js" {
     import { IExecPipe } from "@qiwi/libdefkit/target/es6/interface.js";
-    export const generate: (tsconfig: string, name: string, cwd: string, entryPoints?: Record<string, string>) => string;
+    export const generate: (tsconfig: string, name: string, cwd: string, entryPoints: Record<string, string>, ext: string) => string;
     export const mixFiles: (files: string[], memo?: string) => string;
     export const pipe: IExecPipe;
 }
@@ -83,6 +85,7 @@ declare module '@qiwi/libdefkitfake' {
 ",
   "dtsOut": "<cwd>/src/test/temp/index.d.ts",
   "entry": "./index.ts",
+  "ext": ".js",
   "flowOut": "<cwd>/src/test/temp/index.flow.js",
   "name": "@qiwi/libdefkit",
   "tsconfig": [