diff --git a/src/cli/index.ts b/src/cli/index.ts
index b9d046bad..5a3892643 100755
--- a/src/cli/index.ts
+++ b/src/cli/index.ts
@@ -1,10 +1,11 @@
 import { build, export as exporter } from 'sapper/core.js';
-import { dest, dev, entry, src } from '../config';
+import { dest, entry, isDev, src } from '../config';
 
 process.env.NODE_ENV = 'production';
 
 const cmd = process.argv[2];
 const start = Date.now();
+const dev = isDev();
 
 if (cmd === 'build') {
 	build({ dest, dev, entry, src })
diff --git a/src/config.ts b/src/config.ts
index f685ca762..310f7f054 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -1,6 +1,6 @@
 import * as path from 'path';
 
-export const dev = process.env.NODE_ENV !== 'production';
+export const isDev = () => process.env.NODE_ENV !== 'production';
 
 export const templates = path.resolve(process.env.SAPPER_TEMPLATES || 'templates');
 export const src = path.resolve(process.env.SAPPER_ROUTES || 'routes');
@@ -9,4 +9,4 @@ export const dest = path.resolve(process.env.SAPPER_DEST || '.sapper');
 export const entry = {
 	client: path.resolve(templates, '.main.rendered.js'),
 	server: path.resolve(dest, 'server-entry.js')
-};
\ No newline at end of file
+};
diff --git a/src/middleware/index.ts b/src/middleware/index.ts
index dfb690058..6e91718b6 100644
--- a/src/middleware/index.ts
+++ b/src/middleware/index.ts
@@ -5,8 +5,10 @@ import rimraf from 'rimraf';
 import serialize from 'serialize-javascript';
 import escape_html from 'escape-html';
 import { create_routes, templates, create_compilers, create_assets } from 'sapper/core.js';
+import { dest, entry, isDev, src } from '../config';
 import create_watcher from './create_watcher';
-import { dest, dev, entry, src } from '../config';
+
+const dev = isDev();
 
 function connect_dev() {
 	mkdirp.sync(dest);
diff --git a/src/webpack/index.ts b/src/webpack/index.ts
index 4cf620ece..c7f398fe1 100644
--- a/src/webpack/index.ts
+++ b/src/webpack/index.ts
@@ -1,7 +1,7 @@
-import { dest, dev, entry } from '../config';
+import { dest, isDev, entry } from '../config';
 
 export default {
-	dev,
+	dev: isDev(),
 
 	client: {
 		entry: () => {