diff --git a/dev-requirements.txt b/dev-requirements.txt
index d61f287d..53eb288e 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -12,8 +12,7 @@ mock
 # nbclassic provides the '/tree/' handler, which we use in tests
 # it is a transitive dependency via jupyterlab,
 # but depend on it directly
-# 0.4 introduces some installation/loading problems (check again after 0.4.3)
-nbclassic<0.4
+nbclassic
 pre-commit
 pytest>=3.3
 pytest-asyncio; python_version < "3.7"
diff --git a/jupyterhub/singleuser/mixins.py b/jupyterhub/singleuser/mixins.py
index 16bd259e..6f52dbfd 100755
--- a/jupyterhub/singleuser/mixins.py
+++ b/jupyterhub/singleuser/mixins.py
@@ -754,7 +754,7 @@ class SingleUserNotebookAppMixin(Configurable):
             if env_name in settings:
                 # when running with jupyter-server, classic notebook (nbclassic server extension or notebook v7)
                 # gets its own jinja env, which needs the same patch
-                jinja_envs.append(settings['notebook_jinja2_env'])
+                jinja_envs.append(settings[env_name])
 
         # patch jinja env loading to get modified template, only for base page.html
         def get_page(name):
diff --git a/jupyterhub/tests/test_singleuser.py b/jupyterhub/tests/test_singleuser.py
index 1a870d59..d41a63f9 100644
--- a/jupyterhub/tests/test_singleuser.py
+++ b/jupyterhub/tests/test_singleuser.py
@@ -195,10 +195,22 @@ def test_singleuser_app_class(JUPYTERHUB_SINGLEUSER_APP):
         import jupyter_server  # noqa
     except ImportError:
         have_server = False
-        expect_error = "jupyter_server" in JUPYTERHUB_SINGLEUSER_APP
     else:
         have_server = True
-        expect_error = False
+    try:
+        import notebook.notebookapp  # noqa
+    except ImportError:
+        have_notebook = False
+    else:
+        have_notebook = True
+
+    if JUPYTERHUB_SINGLEUSER_APP.startswith("notebook."):
+        expect_error = not have_notebook
+    elif JUPYTERHUB_SINGLEUSER_APP.startswith("jupyter_server."):
+        expect_error = not have_server
+    else:
+        # not specified, will try both
+        expect_error = not (have_server or have_notebook)
 
     if expect_error:
         ctx = pytest.raises(CalledProcessError)