diff --git a/package.json b/package.json
index 6f5fb1a..230039c 100644
--- a/package.json
+++ b/package.json
@@ -47,7 +47,7 @@
   },
   "homepage": "https://github.com/rollup/rollup",
   "devDependencies": {
-    "acorn": "^3.2.0",
+    "acorn": "^4.0.1",
     "buble": "^0.12.5",
     "chalk": "^1.1.3",
     "codecov.io": "^0.1.6",
diff --git a/rollup.config.js b/rollup.config.js
index f55dc7c..a8ac2c8 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -22,11 +22,7 @@ export default {
 	entry: 'src/rollup.js',
 	plugins: [
 		buble({
-			include: [ 'node_modules/acorn/**' ]
-		}),
-
-		buble({
-			include: [ 'src/**' ],
+			include: [ 'src/**', 'node_modules/acorn/**' ],
 			target: {
 				node: 4
 			}
diff --git a/test/function/double-default-export/_config.js b/test/function/double-default-export/_config.js
index 26e86e7..d5f5254 100644
--- a/test/function/double-default-export/_config.js
+++ b/test/function/double-default-export/_config.js
@@ -1,8 +1,9 @@
+const path = require( 'path' );
 const assert = require( 'assert' );
 
 module.exports = {
 	description: 'throws on double default exports',
 	error: err => {
-		assert.equal( err.message, 'A module can only have one default export' );
+		assert.equal( err.message, `Duplicate export 'default' (2:7) in ${path.resolve(__dirname, 'foo.js')}` );
 	}
 };
diff --git a/test/function/double-named-export/_config.js b/test/function/double-named-export/_config.js
index 577b421..169ce76 100644
--- a/test/function/double-named-export/_config.js
+++ b/test/function/double-named-export/_config.js
@@ -1,8 +1,9 @@
+const path = require( 'path' );
 const assert = require( 'assert' );
 
 module.exports = {
 	description: 'throws on duplicate named exports',
 	error: err => {
-		assert.equal( err.message, `A module cannot have multiple exports with the same name ('foo')` );
+		assert.equal( err.message, `Duplicate export 'foo' (3:9) in ${path.resolve(__dirname, 'foo.js')}` );
 	}
 };
diff --git a/test/function/double-named-reexport/_config.js b/test/function/double-named-reexport/_config.js
index 577b421..169ce76 100644
--- a/test/function/double-named-reexport/_config.js
+++ b/test/function/double-named-reexport/_config.js
@@ -1,8 +1,9 @@
+const path = require( 'path' );
 const assert = require( 'assert' );
 
 module.exports = {
 	description: 'throws on duplicate named exports',
 	error: err => {
-		assert.equal( err.message, `A module cannot have multiple exports with the same name ('foo')` );
+		assert.equal( err.message, `Duplicate export 'foo' (3:9) in ${path.resolve(__dirname, 'foo.js')}` );
 	}
 };