diff --git a/lib/index.js b/lib/index.js
index 808d421..67d6ed5 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -20,7 +20,6 @@ function render({ filename, files, metadata, engineOptions }) {
   // Stop if the current extension can't be transformed
   if (!transform) {
     debug(`no transformer available for ${ext} extension for ${filename}`);
-    extensions.push(ext);
     return Promise.resolve();
   }
 
diff --git a/lib/index.test.js b/lib/index.test.js
index 03e251e..9f59014 100644
--- a/lib/index.test.js
+++ b/lib/index.test.js
@@ -236,4 +236,26 @@ describe('metalsmith-in-place', () => {
       done();
     });
   });
+
+  it('should allow extending with pug templates', done => {
+    const base = path.join(
+      process.cwd(),
+      'test',
+      'fixtures',
+      'ignore-extension-without-jstransformer'
+    );
+    const actual = path.join(base, 'build');
+    const expected = path.join(base, 'expected');
+    const metalsmith = new Metalsmith(base);
+
+    rimraf.sync(actual);
+
+    return metalsmith.use(plugin()).build(err => {
+      if (err) {
+        return done(err);
+      }
+      expect(() => equal(actual, expected)).not.toThrow();
+      return done();
+    });
+  });
 });