diff --git a/jupyterhub/auth.py b/jupyterhub/auth.py
index 33a00bef..09d09a02 100644
--- a/jupyterhub/auth.py
+++ b/jupyterhub/auth.py
@@ -1101,6 +1101,13 @@ class PAMAuthenticator(LocalAuthenticator):
         else:
             return super().normalize_username(username)
 
+    def get_custom_html(self, base_url):
+        """Get custom HTML for the authenticator.
+
+        .. versionadded: 1.4
+        """
+        return self.custom_html
+
 
 for _old_name, _new_name, _version in [
     ("check_group_whitelist", "check_group_allowed", "1.2"),
diff --git a/jupyterhub/handlers/login.py b/jupyterhub/handlers/login.py
index 605cd580..29f2ff02 100644
--- a/jupyterhub/handlers/login.py
+++ b/jupyterhub/handlers/login.py
@@ -3,6 +3,7 @@
 # Distributed under the terms of the Modified BSD License.
 import asyncio
 
+from jinja2 import Template
 from tornado import web
 from tornado.escape import url_escape
 from tornado.httputil import url_concat
@@ -90,17 +91,23 @@ class LoginHandler(BaseHandler):
     """Render the login page."""
 
     def _render(self, login_error=None, username=None):
-        return self.render_template(
-            'login.html',
-            next=url_escape(self.get_argument('next', default='')),
-            username=username,
-            login_error=login_error,
-            custom_html=self.authenticator.custom_html,
-            login_url=self.settings['login_url'],
-            authenticator_login_url=url_concat(
+        context = {
+            "next": url_escape(self.get_argument('next', default='')),
+            "username": username,
+            "login_error": login_error,
+            "login_url": self.settings['login_url'],
+            "authenticator_login_url": url_concat(
                 self.authenticator.login_url(self.hub.base_url),
                 {'next': self.get_argument('next', '')},
             ),
+        }
+        custom_html = Template(
+            self.authenticator.get_custom_html(self.hub.base_url)
+        ).render(**context)
+        return self.render_template(
+            'login.html',
+            **context,
+            custom_html=custom_html,
         )
 
     async def get(self):