diff --git a/flask_s3.py b/flask_s3.py
index 6298cda..c03cbc7 100644
--- a/flask_s3.py
+++ b/flask_s3.py
@@ -26,7 +26,10 @@ def url_for(endpoint, **values):
     app = current_app
     if 'S3_BUCKET_NAME' not in app.config:
         raise ValueError("S3_BUCKET_NAME not found in app configuration.")
-
+    
+    if app.debug and not app.config['USE_S3_DEBUG']:
+        return flask_url_for(endpoint, **values)
+    
     if endpoint == 'static' or endpoint.endswith('.static'):
         scheme = 'http'
         if app.config['S3_USE_HTTPS']:
@@ -189,6 +192,5 @@ class FlaskS3(object):
             app.config.setdefault(k, v)
 
         if app.config['USE_S3']:
-            if not app.debug or app.config['USE_S3_DEBUG']:
-                app.jinja_env.globals['url_for'] = url_for
+            app.jinja_env.globals['url_for'] = url_for
 
diff --git a/tests/test_flask_static.py b/tests/test_flask_static.py
index 34ba24b..12135ac 100644
--- a/tests/test_flask_static.py
+++ b/tests/test_flask_static.py
@@ -84,6 +84,17 @@ class UrlTests(unittest.TestCase):
         exp = 'https://foo.s3.amazonaws.com/static/bah.js'
         self.assertEquals(self.client_get(ufs).data, exp)
 
+    def test_url_for_debug(self):
+        """Tests Flask-S3 behaviour in debug mode."""
+        self.app.debug = True
+        # static endpoint url_for in template
+        ufs = "{{url_for('static', filename='bah.js')}}"
+        exp = '/static/bah.js'
+        self.assertEquals(self.client_get(ufs).data, exp)
+        self.app.config['USE_S3_DEBUG'] = True
+        exp = 'https://foo.s3.amazonaws.com/static/bah.js'
+        self.assertEquals(self.client_get(ufs).data, exp)
+
     def test_url_for_blueprint(self):
         """Tests that correct url formed for static asset in blueprint."""
         # static endpoint url_for in template