diff --git a/src/cli.js b/src/cli.js
index 6edfcd23d58a1346a773e5d739d21778be39c941..cbddc609aaa78da04b410b45dddf75980785a062 100644
--- a/src/cli.js
+++ b/src/cli.js
@@ -54,7 +54,10 @@ const cli = {
       // Show help
       console.log(options.generateHelp());
     } else {
-      const configuration = { extensions };
+      const configuration = { };
+      if (extensions) {
+        configuration.extensions = extensions;
+      }
       if (configFile) {
         configuration.overrideConfigFile = configFile;
       }
diff --git a/src/config/options.js b/src/config/options.js
index dac85019bac496b5bae6a0d27f44b92ec91af71b..87e43089afcb0b0ece161a050cc776fae56c5fc2 100644
--- a/src/config/options.js
+++ b/src/config/options.js
@@ -32,7 +32,7 @@ module.exports = optionator({
   }, {
     option     : 'ext',
     type       : '[String]',
-    default    : '.js',
+    default    : '',
     description: 'Specify JavaScript file extensions'
   }, {
     option     : 'config',