diff --git a/dist/server/build.js b/dist/server/build.js
index 0c892edb1249..5e158c9f22d1 100644
--- a/dist/server/build.js
+++ b/dist/server/build.js
@@ -59,7 +59,7 @@ _shelljs2.default.mkdir('-p', _path2.default.resolve(outputDir, 'static'));
 // Build the webpack configuration using the `baseConfig`
 // custom `.babelrc` file and `webpack.config.js` files
 var configDir = _commander2.default.configDir || './.storybook';
-var config = (0, _config2.default)(_webpackConfig2.default, configDir);
+var config = (0, _config2.default)('PRODUCTION', _webpackConfig2.default, configDir);
 
 // Write both the storybook UI and IFRAME HTML files to destination path.
 var headHtml = (0, _utils.getHeadHtml)(configDir);
diff --git a/dist/server/config.js b/dist/server/config.js
index 1ba90f34e6e7..e317bdaef982 100644
--- a/dist/server/config.js
+++ b/dist/server/config.js
@@ -12,7 +12,7 @@ var _extends2 = require('babel-runtime/helpers/extends');
 
 var _extends3 = _interopRequireDefault(_extends2);
 
-exports.default = function (baseConfig, configDir) {
+exports.default = function (configType, baseConfig, configDir) {
   var config = baseConfig;
 
   // search for a .babelrc in the config directory, then the module root directory
@@ -56,7 +56,7 @@ exports.default = function (baseConfig, configDir) {
 
   if (typeof customConfig === 'function') {
     logger.info('=> Loading custom webpack config (full-control mode).');
-    return customConfig(config);
+    return customConfig(config, configType);
   }
 
   logger.info('=> Loading custom webpack config.');
diff --git a/dist/server/index.js b/dist/server/index.js
index 214eb8ae75bf..b4cd20198418 100755
--- a/dist/server/index.js
+++ b/dist/server/index.js
@@ -81,7 +81,7 @@ if (_commander2.default.staticDir) {
 // Build the webpack configuration using the `baseConfig`
 // custom `.babelrc` file and `webpack.config.js` files
 var configDir = _commander2.default.configDir || './.storybook';
-var config = (0, _config2.default)(_webpack4.default, configDir);
+var config = (0, _config2.default)('DEVELOPMENT', _webpack4.default, configDir);
 
 var compiler = (0, _webpack2.default)(config);
 var devMiddlewareOptions = {
diff --git a/src/server/build.js b/src/server/build.js
index a09fbabf9358..2c73e62dc0ac 100644
--- a/src/server/build.js
+++ b/src/server/build.js
@@ -31,7 +31,7 @@ shelljs.mkdir('-p', path.resolve(outputDir, 'static'));
 // Build the webpack configuration using the `baseConfig`
 // custom `.babelrc` file and `webpack.config.js` files
 const configDir = program.configDir || './.storybook';
-const config = loadConfig(baseConfig, configDir);
+const config = loadConfig('PRODUCTION', baseConfig, configDir);
 
 // Write both the storybook UI and IFRAME HTML files to destination path.
 const headHtml = getHeadHtml(configDir);
diff --git a/src/server/config.js b/src/server/config.js
index f5b26cc6c5e2..77d03803429d 100644
--- a/src/server/config.js
+++ b/src/server/config.js
@@ -25,7 +25,7 @@ function loadBabelConfig(babelConfigPath) {
 // `baseConfig` is a webpack configuration bundled with storybook.
 // React Storybook will look in the `configDir` directory
 // (inside working directory) if a config path is not provided.
-export default function (baseConfig, configDir) {
+export default function (configType, baseConfig, configDir) {
   const config = baseConfig;
 
   // search for a .babelrc in the config directory, then the module root directory
@@ -69,7 +69,7 @@ export default function (baseConfig, configDir) {
 
   if (typeof customConfig === 'function') {
     logger.info('=> Loading custom webpack config (full-control mode).');
-    return customConfig(config);
+    return customConfig(config, configType);
   }
 
   logger.info('=> Loading custom webpack config.');
diff --git a/src/server/index.js b/src/server/index.js
index 59862615138a..981ee53d11cc 100755
--- a/src/server/index.js
+++ b/src/server/index.js
@@ -47,7 +47,7 @@ if (program.staticDir) {
 // Build the webpack configuration using the `baseConfig`
 // custom `.babelrc` file and `webpack.config.js` files
 const configDir = program.configDir || './.storybook';
-const config = loadConfig(baseConfig, configDir);
+const config = loadConfig('DEVELOPMENT', baseConfig, configDir);
 
 const compiler = webpack(config);
 const devMiddlewareOptions = {