diff --git a/.travis.yml b/.travis.yml
index a1cbe42..144a067 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,26 +1,44 @@
 language: python
-python:
-  - "2.7"
-  - "3.6"
-  - "3.7"
+
 # necessary for python 3.7, see https://github.com/travis-ci/travis-ci/issues/9815
 dist: xenial
-sudo: yes
-env:
-  - SPHINX_VERSION=1.5.*
-  - SPHINX_VERSION=1.6.*
-  - SPHINX_VERSION=1.7.*
-  - SPHINX_VERSION=1.8.*
-  - SPHINX_VERSION=2.0.*
-  - SPHINX_VERSION=""
-matrix:
-  exclude:
-    - python: "2.7"
+
+jobs:
+  include:
+    - python: "3.8"
+      env: SPHINX_VERSION=2.4.*
+    - python: "3.8"
+      env: SPHINX_VERSION=3.0.*
+    - python: "3.8"
+      env: SPHINX_VERSION=""
+    - python: "3.7"
+      env: SPHINX_VERSION=1.7.*
+    - python: "3.7"
+      env: SPHINX_VERSION=1.8.*
+    - python: "3.7"
       env: SPHINX_VERSION=2.0.*
     - python: "3.7"
-      env: SPHINX_VERSION=1.5.*
+      env: SPHINX_VERSION=2.1.*
+    - python: "3.7"
+      env: SPHINX_VERSION=2.2.*
+    - python: "3.7"
+      env: SPHINX_VERSION=2.3.*
     - python: "3.7"
+      env: SPHINX_VERSION=2.4.*
+    - python: "3.7"
+      env: SPHINX_VERSION=3.0.*
+    - python: "3.7"
+      env: SPHINX_VERSION=""
+    - python: "2.7"
+      env: SPHINX_VERSION=1.5.*
+    - python: "2.7"
       env: SPHINX_VERSION=1.6.*
+    - python: "2.7"
+      env: SPHINX_VERSION=1.7.*
+    - python: "2.7"
+      env: SPHINX_VERSION=1.8.*
+    - python: "2.7"
+      env: SPHINX_VERSION=""
 addons:
   apt:
     packages:
diff --git a/sphinx_nbexamples/__init__.py b/sphinx_nbexamples/__init__.py
index d65a870..0140afe 100644
--- a/sphinx_nbexamples/__init__.py
+++ b/sphinx_nbexamples/__init__.py
@@ -1162,7 +1162,10 @@ def setup(app):
 
     app.add_config_value('example_gallery_config', gallery_config, 'html')
 
-    app.add_stylesheet('example_gallery_styles.css')
+    if int(sphinx.__version__.split('.')[0]) >= 3:
+        app.add_css_file('example_gallery_styles.css')
+    else:
+        app.add_stylesheet('example_gallery_styles.css')
 
     app.add_directive('linkgalleries', LinkGalleriesDirective)
 
diff --git a/tests/test_sphinx_nbexamples.py b/tests/test_sphinx_nbexamples.py
index 57f257b..b888378 100644
--- a/tests/test_sphinx_nbexamples.py
+++ b/tests/test_sphinx_nbexamples.py
@@ -48,6 +48,7 @@ def setUp(self):
         os.rmdir(self.src_dir)
         self.out_dir = osp.join(self.src_dir, 'build', 'html')
         shutil.copytree(sphinx_supp, self.src_dir)
+
         self.app = Sphinx(
             srcdir=self.src_dir, confdir=self.src_dir, outdir=self.out_dir,
             doctreedir=osp.join(self.src_dir, 'build', 'doctrees'),
@@ -219,6 +220,27 @@ def test_bash(self):
         self.assertIn('hello, world', rst)
 
 
+class TestWarnings(BaseTest):
+
+    def setUp(self):
+        pass
+
+    def _setUp(self):
+        super().setUp()
+
+    @unittest.skipIf(int(sphinx.__version__.split('.')[0]) != 3,
+                     "Test implemented for sphinx 3.0")
+    @unittest.expectedFailure
+    def test_stylesheet_warning(self):
+        """Test whether the app.add_stylesheet() warning is triggered
+
+        See https://github.com/Chilipp/sphinx-nbexamples/issues/14"""
+        from sphinx.application import RemovedInSphinx40Warning
+        self.assertWarnsRegex(
+            RemovedInSphinx40Warning, '.*Please use app.add_css_file',
+            self._setUp)
+
+
 @unittest.skipIf(pathlib is None, 'The pathlib package is required!')
 class TestLinkGalleries(BaseTest):