diff --git a/lms/djangoapps/courseware/tests/test_courses.py b/lms/djangoapps/courseware/tests/test_courses.py
index ffb2a0dcc3..9cb46095d1 100644
--- a/lms/djangoapps/courseware/tests/test_courses.py
+++ b/lms/djangoapps/courseware/tests/test_courses.py
@@ -443,3 +443,17 @@ class TestGetCourseAssignments(CompletionWaffleTestMixin, ModuleStoreTestCase):
         assignments = get_course_assignments(course.location.context_key, self.user, None)
         assert len(assignments) == 1
         assert assignments[0].complete
+
+    def test_completion_does_not_count_empty_sequentials(self):
+        """
+        Test that we treat a sequential with no content as incomplete.
+
+        This can happen with unreleased assignments, for example (start date in future).
+        """
+        course = CourseFactory()
+        chapter = ItemFactory(parent=course, category='chapter', graded=True, due=datetime.datetime.now())
+        ItemFactory(parent=chapter, category='sequential')
+
+        assignments = get_course_assignments(course.location.context_key, self.user, None)
+        assert len(assignments) == 1
+        assert not assignments[0].complete
diff --git a/openedx/features/course_experience/utils.py b/openedx/features/course_experience/utils.py
index 1968174c69..023df00f47 100644
--- a/openedx/features/course_experience/utils.py
+++ b/openedx/features/course_experience/utils.py
@@ -214,6 +214,15 @@ def is_block_structure_complete_for_assignments(block_data, block_key):
     if children:
         return all(is_block_structure_complete_for_assignments(block_data, child_key) for child_key in children)
 
+    category = block_data.get_xblock_field(block_key, 'category')
+    if category in ('course', 'chapter', 'sequential', 'vertical'):
+        # If there are no children for these "hierarchy" block types, just bail. This could be because the
+        # content isn't available yet (start date in future) or we're too late and the block has hide_after_due
+        # set. Or maybe a different transformer cut off content for whatever reason. Regardless of the cause - if the
+        # user can't see this content and we continue, we might accidentally say this block is complete because it
+        # isn't scored (which most hierarchy blocks wouldn't be).
+        return False
+
     complete = block_data.get_xblock_field(block_key, 'complete', False)
     graded = block_data.get_xblock_field(block_key, 'graded', False)
     has_score = block_data.get_xblock_field(block_key, 'has_score', False)