diff --git a/tools/run-mypy b/tools/run-mypy
index 46b02e892b..c5c9773265 100755
--- a/tools/run-mypy
+++ b/tools/run-mypy
@@ -47,7 +47,6 @@ zerver/management/commands/enqueue_file.py
 zerver/management/commands/rename_stream.py
 zerver/management/commands/runtornado.py
 zerver/tests/test_i18n.py
-zerver/views/__init__.py
 zerver/views/messages.py
 zerver/views/webhooks/beanstalk.py
 """.split()
diff --git a/zerver/views/__init__.py b/zerver/views/__init__.py
index b0d12a2bf7..21a1694ab6 100644
--- a/zerver/views/__init__.py
+++ b/zerver/views/__init__.py
@@ -50,6 +50,7 @@ from zerver.decorator import require_post, authenticated_json_post_view, \
 from zerver.lib.avatar import avatar_url
 from zerver.lib.response import json_success, json_error
 from zerver.lib.utils import statsd, generate_random_token
+from zerver.lib.str_utils import force_str
 from zproject.backends import password_auth_enabled, dev_auth_enabled, google_auth_enabled
 
 from confirmation.models import Confirmation, RealmCreationKey, check_key_is_valid
@@ -304,7 +305,7 @@ def webathena_kerberos_login(request, user_profile,
                                "/home/zulip/zulip/bots/process_ccache",
                                user,
                                user_profile.api_key,
-                               base64.b64encode(ccache)])
+                               force_str(base64.b64encode(ccache))])
     except Exception:
         logging.exception("Error updating the user's ccache")
         return json_error(_("We were unable to setup mirroring for you"))