diff --git a/packages/gatsby/src/utils/webpack.config.js b/packages/gatsby/src/utils/webpack.config.js
index 788b40a22a58c..bbbe3c862fc04 100644
--- a/packages/gatsby/src/utils/webpack.config.js
+++ b/packages/gatsby/src/utils/webpack.config.js
@@ -372,7 +372,7 @@ module.exports = async (
     // Common config for every env.
     config.loader(`js`, {
       test: /\.jsx?$/, // Accept either .js or .jsx files.
-      exclude: /(node_modules|bower_components)/,
+      exclude: [/(node_modules|bower_components)/],
       loader: `babel`,
       query: babelConfig,
     })
@@ -409,7 +409,7 @@ module.exports = async (
       case `develop`:
         config.loader(`css`, {
           test: /\.css$/,
-          exclude: /\.module\.css$/,
+          exclude: [/\.module\.css$/],
           loaders: [`style`, `css`, `postcss`],
         })
 
@@ -434,7 +434,7 @@ module.exports = async (
       case `build-css`:
         config.loader(`css`, {
           test: /\.css$/,
-          exclude: /\.module\.css$/,
+          exclude: [/\.module\.css$/],
           loader: ExtractTextPlugin.extract([`css?minimize`, `postcss`]),
         })
 
@@ -464,7 +464,7 @@ module.exports = async (
 
         config.loader(`css`, {
           test: /\.css$/,
-          exclude: /\.module\.css$/,
+          exclude: [/\.module\.css$/],
           loader: `null`,
         })
 
@@ -489,7 +489,7 @@ module.exports = async (
 
         config.loader(`css`, {
           test: /\.css$/,
-          exclude: /\.module\.css$/,
+          exclude: [/\.module\.css$/],
           // loader: `null`,
           loader: ExtractTextPlugin.extract([`css`]),
         })