diff --git a/python/install.py b/python/install.py
index 857b2b1..15dcfc8 100644
--- a/python/install.py
+++ b/python/install.py
@@ -76,4 +76,4 @@ def main(argv=None):
 
 
 if __name__ == '__main__':
-    main()
\ No newline at end of file
+    main()
diff --git a/src/converter.ts b/src/converter.ts
index 45d235e..373e889 100644
--- a/src/converter.ts
+++ b/src/converter.ts
@@ -67,7 +67,7 @@ export interface CompletionInfo {
   candidates: string[];
   /**
    * The original completion from TS compiler.
-   * It's exposed for debugging purpuse.
+   * It's exposed for debugging purpose.
    */
   original?: ts.CompletionInfo;
 }
@@ -78,12 +78,14 @@ export interface IsCompleteResult {
 }
 
 export interface ConverterOptions {
-  /** If true, JavaScript mode. TypeSceript mode otherwise */
+  /** If true, JavaScript mode. TypeScript mode otherwise */
   isJS?: boolean;
   /** If true, creates a converter for browser mode. Otherwise, Node.js */
   isBrowser?: boolean;
   /** Only for testing. File changes are forwarded to this handler. */
   _fileWatcher?: ts.FileWatcherCallback;
+  /** If specified target will be used */
+  target?: string;
 }
 
 export interface Converter {
@@ -117,17 +119,17 @@ export function createConverter(options?: ConverterOptions): Converter {
   const dstFilename = normalizeJoin(outDir, "__tslab__.js");
   const dstDeclFilename = normalizeJoin(outDir, "__tslab__.d.ts");
 
+  const transpileTargetOption = ts.ScriptTarget[options?.target];
   // c.f.
   // https://github.com/microsoft/TypeScript/wiki/Node-Target-Mapping
   // https://github.com/microsoft/TypeScript/issues/22306#issuecomment-412266626
-  const transpileTarget =
-    semver.major(process.version) >= 12
+  const transpileTarget = transpileTargetOption ??
+    (semver.major(process.version) >= 12
       ? ts.ScriptTarget.ES2019
-      : ts.ScriptTarget.ES2018;
+      : ts.ScriptTarget.ES2018);
   // References:
   // https://github.com/microsoft/TypeScript/blob/master/src/lib/es2019.full.d.ts
-  const transpileLib =
-    transpileTarget === ts.ScriptTarget.ES2019 ? ["es2019"] : ["es2018"];
+  const transpileLib = [ ts.ScriptTarget[transpileTarget] ];
   if (options?.isBrowser) {
     transpileLib.push("dom");
     transpileLib.push("dom.iterable");
diff --git a/src/main.ts b/src/main.ts
index 61143b6..9951208 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -11,19 +11,21 @@ class ConverterSetImpl implements ConverterSet {
   private jsKernel: boolean;
   private _node: Converter;
   private _browser: Converter;
+  private target?: string;
 
-  constructor(jsKernel: boolean) {
+  constructor(jsKernel: boolean, target?: string) {
     this.jsKernel = jsKernel;
+    this.target = target;
   }
   get node(): Converter {
     if (!this._node) {
-      this._node = createConverter({ isJS: this.jsKernel, isBrowser: false });
+      this._node = createConverter({ isJS: this.jsKernel, isBrowser: false, target: this.target });
     }
     return this._node;
   }
   get browser(): Converter {
     if (!this._browser) {
-      this._browser = createConverter({ isJS: this.jsKernel, isBrowser: true });
+      this._browser = createConverter({ isJS: this.jsKernel, isBrowser: true, target: this.target });
     }
     return this._browser;
   }
@@ -83,15 +85,16 @@ export function startKernel({
   enableFindLocal = true,
   jsKernel = false,
   globalVersion = "",
+  target,
 }): void {
   if (enableFindLocal) {
     const local = findLocalStartKernel();
     if (local) {
-      local({ configPath, enableFindLocal: false, jsKernel, globalVersion });
+      local({ configPath, enableFindLocal: false, jsKernel, globalVersion, target });
       return;
     }
   }
-  const convs = new ConverterSetImpl(jsKernel);
+  const convs = new ConverterSetImpl(jsKernel, target);
   convs.node; // Warm the converter for Node.js
   const executor = createExecutor(process.cwd(), convs, {
     log: console.log,
@@ -145,17 +148,8 @@ export function main() {
       "--prefix [prefix]",
       "Kernelspec will be installed in {PREFIX}/share/jupyter/kernels/"
     )
-    .action(function () {
-      if (arguments.length != 1) {
-        console.error(
-          "Unused args:",
-          Array.from(arguments).filter((arg) => {
-            return typeof arg === "string";
-          })
-        );
-        process.exit(1);
-      }
-      let { binary, python, user, sysPrefix, prefix } = arguments[0];
+    .action(function (options) {
+      const { binary, python, user, sysPrefix, prefix } = options;
       const args = [path.join(path.dirname(__dirname), "python", "install.py")];
       args.push(`--tslab=${binary}`);
       if (user) {
@@ -184,18 +178,10 @@ export function main() {
     .description("Start Jupyter kernel. Used from Jupyter internally")
     .option("--config-path <path>", "Path of config file")
     .option("--js", "If set, start JavaScript kernel. Otherwise, TypeScript.")
-    .action(function () {
-      if (arguments.length != 1) {
-        console.error(
-          "Unused args:",
-          Array.from(arguments).filter((arg) => {
-            return typeof arg === "string";
-          })
-        );
-        process.exit(1);
-      }
-      let { configPath, js: jsKernel } = arguments[0];
-      startKernel({ configPath, jsKernel, globalVersion: getVersion() });
+    .option("-t, --target [target]", "If set, target will be used by transpiler.")
+    .action(function (options) {
+      const { configPath, js: jsKernel, target } = options;
+      startKernel({ configPath, jsKernel, globalVersion: getVersion(), target });
     });
 
   program.parse(process.argv);