diff --git a/packages/pegjs/lib/compiler/index.js b/packages/pegjs/lib/compiler/index.js
index 4d44bd4..dd35d7d 100644
--- a/packages/pegjs/lib/compiler/index.js
+++ b/packages/pegjs/lib/compiler/index.js
@@ -67,8 +67,8 @@ const compiler = {
             trace: false
         } );
 
-        // We want `session.vm.runInContext` to return the parser
-        if ( options.output === "parser" ) options.format = "bare";
+        // We want `session.vm.evalModule` to return the parser
+        if ( options.output === "parser" ) options.format = "umd";
 
         util.each( session.passes, stage => {
 
@@ -83,7 +83,7 @@ const compiler = {
         switch ( options.output ) {
 
             case "parser":
-                return session.vm.runInContext( ast.code, options.context );
+                return session.vm.evalModule( ast.code, options.context );
 
             case "source":
                 return ast.code;
diff --git a/packages/pegjs/lib/compiler/session.js b/packages/pegjs/lib/compiler/session.js
index e26bc63..30a92d6 100644
--- a/packages/pegjs/lib/compiler/session.js
+++ b/packages/pegjs/lib/compiler/session.js
@@ -7,6 +7,7 @@ const GrammarError = require( "../grammar-error" );
 const opcodes = require( "./opcodes" );
 const parser = require( "../parser" );
 const util = require( "../util" );
+const vm = require( "../util/vm" );
 
 function fatal( message, location ) {
 
@@ -28,9 +29,7 @@ class Session {
         this.parser = config.parser || parser;
         this.passes = config.passes || {};
         this.visitor = config.visitor || ast.visitor;
-        this.vm = config.vm || {
-            runInContext: util.runInContext
-        };
+        this.vm = config.vm || vm;
 
         if ( typeof config.warn === "function" ) this.warn = config.warn;
         if ( typeof config.error === "function" ) this.error = config.error;
diff --git a/packages/pegjs/lib/util/vm.js b/packages/pegjs/lib/util/vm.js
index 4e9beaa..d21b62c 100644
--- a/packages/pegjs/lib/util/vm.js
+++ b/packages/pegjs/lib/util/vm.js
@@ -1,26 +1,25 @@
 "use strict";
 
 /**
- * `eval` the given source, using properties found in `context` as top-level variables.
+ * `eval` the given source as a CommonJS module, using properties found in `context` as top-level variables.
  * 
  * Based on `vm.runInContext` found in Node.js, this is a cross-env solution.
  */
-function runInContext( source, context ) {
+function evalModule( source, context ) {
 
     const argumentKeys = Object.keys( context );
     const argumentValues = argumentKeys.map( argument => context[ argument ] );
 
-    const object = {};
-    argumentKeys.push( "_peg$object", `_peg$object.result = ${ source };` );
-    argumentValues.push( object );
+    const sandbox = { exports: {} };
+    argumentKeys.push( "module", "exports", source );
+    argumentValues.push( sandbox, sandbox.exports );
 
     Function( ...argumentKeys )( ...argumentValues );
 
-    return object.result;
-
+    return sandbox.exports;
 
 }
 
 // Exports
 
-module.exports = { runInContext };
+module.exports = { evalModule };
diff --git a/packages/pegjs/typings/api.d.ts b/packages/pegjs/typings/api.d.ts
index defcc37..cae3426 100644
--- a/packages/pegjs/typings/api.d.ts
+++ b/packages/pegjs/typings/api.d.ts
@@ -435,7 +435,7 @@ declare namespace peg {
 
         interface ISessionVM {
 
-            runInContext( code: string, context?: { [ name: string ]: any; } ): any;
+            evalModule( code: string, context?: { [ name: string ]: any; } ): any;
 
         }
 
diff --git a/test/spec/api/plugin-api.spec.js b/test/spec/api/plugin-api.spec.js
index 9873f12..de3e610 100644
--- a/test/spec/api/plugin-api.spec.js
+++ b/test/spec/api/plugin-api.spec.js
@@ -131,7 +131,7 @@ describe( "plugin API", function () {
 
                     function pass( ast ) {
 
-                        ast.code = "({ parse: function() { return 42; } })";
+                        ast.code = "exports.parse = function() { return 42; }";
 
                     }