diff --git a/course/constants.py b/course/constants.py
index 7c50b9f1469457c7144366370680fdf7e1eba3b1..f418746b796327abd60311e4fbd1040f3fcd62bf 100644
--- a/course/constants.py
+++ b/course/constants.py
@@ -24,6 +24,8 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 """
 
+if False:
+    import typing  # noqa
 
 from django.utils.translation import pgettext_lazy, ugettext
 # Allow 10x extra credit at the very most.
@@ -286,7 +288,7 @@ FLOW_SESSION_EXPIRATION_MODE_CHOICES = (
 
 
 def is_expiration_mode_allowed(expmode, permissions):
-    # type: (str, frozenset[str]) -> bool
+    # type: (str, typing.FrozenSet[str]) -> bool
     if expmode == flow_session_expiration_mode.roll_over:
         if (flow_permission.set_roll_over_expiration_mode
                 in permissions):
diff --git a/course/content.py b/course/content.py
index 407d1adadbfbb2730847d9917044a40141b3049e..9d320f6c2c75cf8f274b234bf643162ffe8b7d64 100644
--- a/course/content.py
+++ b/course/content.py
@@ -24,7 +24,7 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 """
 
-from typing import cast, Union
+from typing import cast, Union, FrozenSet
 
 from django.conf import settings
 from django.utils.translation import ugettext as _
@@ -1215,7 +1215,7 @@ def compute_chunk_weight_and_shown(
         chunk,  # type: ChunkDesc
         roles,  # type: List[Text]
         now_datetime,  # type: datetime.datetime
-        facilities,  # type: frozenset[Text]
+        facilities,  # type: FrozenSet[Text]
         ):
     # type: (...) -> Tuple[float, bool]
     if not hasattr(chunk, "rules"):
@@ -1274,7 +1274,7 @@ def get_processed_page_chunks(
         page_desc,  # type: StaticPageDesc
         roles,  # type: List[Text]
         now_datetime,  # type: datetime.datetime
-        facilities,  # type: frozenset[Text]
+        facilities,  # type: FrozenSet[Text]
         ):
     # type: (...) -> List[ChunkDesc]
     for chunk in page_desc.chunks:
diff --git a/course/enrollment.py b/course/enrollment.py
index abad304680fc9c9997af018d9f19ac667c37d82c..cd8ee4d3ca2088b1f2ba6e971e2f1b6417f1704e 100644
--- a/course/enrollment.py
+++ b/course/enrollment.py
@@ -71,7 +71,7 @@ from pytools.lex import RE as REBase  # noqa
 # {{{ for mypy
 
 if False:
-    from typing import Any, Tuple, Text, Optional, List  # noqa
+    from typing import Any, Tuple, Text, Optional, List, FrozenSet  # noqa
     from course.utils import CoursePageContext  # noqa
 
 # }}}
@@ -137,7 +137,7 @@ def get_participation_permissions(
         course,  # type: Course
         participation,  # type: Optional[Participation]
         ):
-    # type: (...) -> frozenset[Tuple[Text, Optional[Text]]]
+    # type: (...) -> FrozenSet[Tuple[Text, Optional[Text]]]
 
     if participation is not None:
         return participation.permissions()
diff --git a/course/flow.py b/course/flow.py
index 9122f44691b192006e584bcacea97777645f3e50..bdac6e171c89845d6502773b0c27147b7049f5c2 100644
--- a/course/flow.py
+++ b/course/flow.py
@@ -88,7 +88,7 @@ from relate.utils import retry_transaction_decorator
 # {{{ mypy
 
 if False:
-    from typing import Any, Optional, Iterable, Tuple, Text, List  # noqa
+    from typing import Any, Optional, Iterable, Tuple, Text, List, FrozenSet  # noqa
     import datetime  # noqa
     from course.models import Course  # noqa
     from course.utils import (  # noqa
@@ -1347,7 +1347,7 @@ def recalculate_session_grade(repo, course, session):
 
 def lock_down_if_needed(
         request,  # type: http.HttpRequest
-        permissions,  # type: frozenset[Text]
+        permissions,  # type: FrozenSet[Text]
         flow_session,  # type: FlowSession
         ):
     # type: (...) -> None
@@ -1607,7 +1607,7 @@ def get_and_check_flow_session(pctx, flow_session_id):
 
 
 def will_receive_feedback(permissions):
-    # type: (frozenset[Text]) -> bool
+    # type: (FrozenSet[Text]) -> bool
 
     return (
             flow_permission.see_correctness in permissions
@@ -1615,14 +1615,14 @@ def will_receive_feedback(permissions):
 
 
 def may_send_email_about_flow_page(permissions):
-    # type: (frozenset[Text]) -> bool
+    # type: (FrozenSet[Text]) -> bool
 
     return flow_permission.send_email_about_flow_page in permissions
 
 
 def get_page_behavior(
         page,  # type: PageBase
-        permissions,  # type: frozenset[Text]
+        permissions,  # type: FrozenSet[Text]
         session_in_progress,  # type: bool
         answer_was_graded,  # type: bool
         generates_grade,  # type: bool
@@ -1679,7 +1679,7 @@ def get_page_behavior(
 
 
 def add_buttons_to_form(form, fpctx, flow_session, permissions):
-    # type: (StyledForm, FlowPageContext, FlowSession, frozenset[Text]) -> StyledForm
+    # type: (StyledForm, FlowPageContext, FlowSession, FrozenSet[Text]) -> StyledForm
 
     from crispy_forms.layout import Submit
     show_save_button = getattr(form, "show_save_button", True)
@@ -2137,7 +2137,7 @@ def post_flow_page(
         flow_session,  # type: FlowSession
         fpctx,  # type: FlowPageContext
         request,  # type: http.HttpRequest
-        permissions,  # type: frozenset[Text]
+        permissions,  # type: FrozenSet[Text]
         generates_grade,  # type: bool
         ):
     # type: (...) -> Tuple[PageBehavior, List[FlowPageVisit], forms.Form, Optional[AnswerFeedback], Any, bool]  # noqa
diff --git a/course/page/base.py b/course/page/base.py
index 4bc5c7eb450d9bac9f36cbb6d009a38beff04471..2a5c3b6e496995950f7361412ceeefe5a0d93ffb 100644
--- a/course/page/base.py
+++ b/course/page/base.py
@@ -44,7 +44,7 @@ from django.conf import settings
 # {{{ mypy
 
 if False:
-    from typing import Text, Optional, Any, Tuple, Dict, Callable  # noqa
+    from typing import Text, Optional, Any, Tuple, Dict, Callable, FrozenSet  # noqa
     from django import http  # noqa
     from course.models import (  # noqa
             Course,
@@ -371,7 +371,7 @@ class PageBase(object):
             )
 
     def get_modified_permissions_for_page(self, permissions):
-        # type: (frozenset[Text]) -> frozenset[Text]
+        # type: (FrozenSet[Text]) -> FrozenSet[Text]
         rw_permissions = set(permissions)
 
         if hasattr(self.page_desc, "access_rules"):
diff --git a/course/utils.py b/course/utils.py
index 2ff1f3f567f611043a31478cbbfad6430d58c8db..2be2311b16d00e92732be2c3788672c8ef5e3c37 100644
--- a/course/utils.py
+++ b/course/utils.py
@@ -58,7 +58,7 @@ from course.page.base import (  # noqa
 # {{{ mypy
 
 if False:
-    from typing import Tuple, List, Text, Iterable, Any, Optional, Union, Dict  # noqa
+    from typing import Tuple, List, Text, Iterable, Any, Optional, Union, Dict, FrozenSet  # noqa
     from relate.utils import Repo_ish  # noqa
     from course.models import (  # noqa
             Course,
@@ -105,7 +105,7 @@ class FlowSessionStartRule(FlowSessionRuleBase):
 class FlowSessionAccessRule(FlowSessionRuleBase):
     def __init__(
             self,
-            permissions,  # type: frozenset[Text]
+            permissions,  # type: FrozenSet[Text]
             message=None,  # type: Optional[Text]
             ):
         # type: (...) -> None
@@ -280,7 +280,7 @@ def get_session_start_rule(
         flow_id,  # type: Text
         flow_desc,  # type: FlowDesc
         now_datetime,  # type: datetime.datetime
-        facilities=None,  # type: Optional[frozenset[Text]]
+        facilities=None,  # type: Optional[FrozenSet[Text]]
         for_rollover=False,  # type: bool
         login_exam_ticket=None,  # type: Optional[ExamTicket]
         ):
@@ -373,7 +373,7 @@ def get_session_access_rule(
         session,  # type: FlowSession
         flow_desc,  # type: FlowDesc
         now_datetime,  # type: datetime.datetime
-        facilities=None,  # type: Optional[frozenset[Text]]
+        facilities=None,  # type: Optional[FrozenSet[Text]]
         login_exam_ticket=None,  # type: Optional[ExamTicket]
         ):
     # type: (...) -> FlowSessionAccessRule
@@ -552,7 +552,7 @@ class CoursePageContext(object):
 
         self.request = request
         self.course_identifier = course_identifier
-        self._permissions_cache = None  # type: Optional[frozenset[Tuple[Text, Optional[Text]]]]  # noqa
+        self._permissions_cache = None  # type: Optional[FrozenSet[Tuple[Text, Optional[Text]]]]  # noqa
         self._role_identifiers_cache = None  # type: Optional[List[Text]]
 
         from course.models import Course  # noqa
@@ -612,7 +612,7 @@ class CoursePageContext(object):
         return self._role_identifiers_cache
 
     def permissions(self):
-        # type: () -> frozenset[Tuple[Text, Optional[Text]]]
+        # type: () -> FrozenSet[Tuple[Text, Optional[Text]]]
         if self.participation is None:
             if self._permissions_cache is not None:
                 return self._permissions_cache