diff --git a/README.md b/README.md
index 1c29045..5888d86 100644
--- a/README.md
+++ b/README.md
@@ -131,7 +131,7 @@ You can tweak the generated parser with several options:
   * `-d`, `--dependency` — makes the parser require a specified dependency (can be specified multiple times)
   * `-e`, `--export-var` — name of a global variable into which the parser object is assigned to when no module loader is detected
   * `--extra-options` — additional options (in JSON format) to pass to `peg.generate`
-  * `-c`, `--config`, `--extra-options-file` — file with additional options (in JSON format) to pass to `peg.generate`
+  * `-c`, `--config`, `--extra-options-file` — file with additional options (in JSON or JavaScript) to pass to `peg.generate`
   * `-f`, `--format` — format of the generated parser: `amd`, `bare`, `commonjs`, `es`, `globals`, `umd` (default: `commonjs`)
   * `-O`, `--optimize` — selects between optimizing the generated parser for parsing speed (`speed`) or code size (`size`) (default: `speed`)
   * `-p`, `--plugin` — makes PEG.js use a specified plugin (can be specified multiple times)
diff --git a/bin/options.js b/bin/options.js
index db44485..976e82a 100644
--- a/bin/options.js
+++ b/bin/options.js
@@ -3,13 +3,13 @@
 const fs = require( "fs" );
 const path = require( "path" );
 const peg = require( "../lib/peg" );
+const util = peg.util;
 
 // Options
 
 let inputFile = null;
 let outputFile = null;
-
-const options = {
+let options = {
     "--": [],
     "cache": false,
     "dependencies": {},
@@ -35,33 +35,32 @@ function abort( message ) {
 
 }
 
-function addExtraOptions( json ) {
+function addExtraOptions( config ) {
+
+    if ( typeof config === "string" ) {
 
-    let extraOptions;
+        try {
 
-    try {
+            config = JSON.parse( config );
 
-        extraOptions = JSON.parse( json );
+        } catch ( e ) {
 
-    } catch ( e ) {
+            if ( ! ( e instanceof SyntaxError ) ) throw e;
+            abort( "Error parsing JSON: " + e.message );
 
-        if ( ! ( e instanceof SyntaxError ) ) throw e;
-        abort( "Error parsing JSON: " + e.message );
+        }
 
     }
-    if ( typeof extraOptions !== "object" ) {
+    if ( typeof config !== "object" ) {
 
         abort( "The JSON with extra options has to represent an object." );
 
     }
 
-    Object
-        .keys( extraOptions )
-        .forEach( key => {
-
-            options[ key ] = extraOptions[ key ];
-
-        } );
+    const extraOptions = {};
+    util.extend( extraOptions, config );
+    util.extend( extraOptions, options );
+    options = extraOptions;
 
 }
 
@@ -112,7 +111,7 @@ function nextArg( option ) {
 
 while ( args.length > 0 ) {
 
-    let json, mod;
+    let config, mod;
     let argument = args.shift();
 
     if ( argument.indexOf( "-" ) === 0 && argument.indexOf( "=" ) > 1 ) {
@@ -168,16 +167,24 @@ while ( args.length > 0 ) {
         case "--config":
         case "--extra-options-file":
             argument = nextArg( "-c/--config/--extra-options-file" );
-            try {
+            if ( path.extname( argument ) === ".js" ) {
 
-                json = fs.readFileSync( argument, "utf8" );
+                config = require( path.resolve( argument ) );
 
-            } catch ( e ) {
+            } else {
 
-                abort( `Can't read from file "${ argument }".` );
+                try {
+
+                    config = fs.readFileSync( argument, "utf8" );
+
+                } catch ( e ) {
+
+                    abort( `Can't read from file "${ argument }".` );
+
+                }
 
             }
-            addExtraOptions( json );
+            addExtraOptions( config );
             break;
 
         case "-f":
diff --git a/bin/usage.js b/bin/usage.js
index f7e7f34..e908e93 100644
--- a/bin/usage.js
+++ b/bin/usage.js
@@ -26,7 +26,7 @@ Options:
                                    (note: repeatable option)
 
     --extra-options-file <file>    File with additional options (in JSON
-                                   format) to pass to peg.generate
+                                   or JavaScript) to pass to peg.generate
                                    (note: repeatable option)
 
 -f, --format <format>              Format of the generated parser:
diff --git a/gulpfile.js b/gulpfile.js
index 745a00c..e23a574 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -34,6 +34,7 @@ function node( args, cb ) {
 task( "lint", () => gulp
     .src( [
         "**/.*rc.js",
+        "bin/*.js",
         "lib/**/*.js",
         "!lib/parser/index.js",
         "test/benchmark/**/*.js",
@@ -41,7 +42,7 @@ task( "lint", () => gulp
         "test/impact",
         "test/spec/**/*.js",
         "test/server/run",
-        "bin/*.js",
+        "src/*.js",
         "gulpfile.js"
     ] )
     .pipe( eslint( { dotfiles: true } ) )
@@ -65,7 +66,7 @@ task( "benchmark", cb => {
 // Generate the grammar parser.
 task( "build:parser", cb => {
 
-    node( "bin/peg src/parser.pegjs -o lib/parser/index.js -c src/config.json", cb );
+    node( "bin/peg src/parser.pegjs -o lib/parser/index.js -c src/pegjs.config.js", cb );
 
 } );
 
diff --git a/src/config.json b/src/config.json
deleted file mode 100644
index 6f3be12..0000000
--- a/src/config.json
+++ /dev/null
@@ -1,7 +0,0 @@
-{
-    "header": "/* eslint-disable */",
-    "dependencies": {
-        "ast": "./ast",
-        "util": "../util"
-    }
-}
diff --git a/src/pegjs.config.js b/src/pegjs.config.js
new file mode 100644
index 0000000..d0d1620
--- /dev/null
+++ b/src/pegjs.config.js
@@ -0,0 +1,14 @@
+"use strict";
+
+module.exports = {
+
+    header: "/* eslint-disable */",
+
+    dependencies: {
+
+        ast: "./ast",
+        util: "../util"
+
+    },
+
+};