diff --git a/lms/djangoapps/courseware/models.py b/lms/djangoapps/courseware/models.py
index 023c13f356..c2742f7e28 100644
--- a/lms/djangoapps/courseware/models.py
+++ b/lms/djangoapps/courseware/models.py
@@ -91,7 +91,7 @@ class StudentModule(models.Model):
     module_type = models.CharField(max_length=32, choices=MODULE_TYPES, default='problem', db_index=True)
 
     # Key used to share state. This is the XBlock usage_id
-    module_state_key = UsageKeyField(max_length=255, db_index=True, db_column='module_id')
+    module_state_key = UsageKeyField(max_length=255, db_column='module_id')
     student = models.ForeignKey(User, db_index=True)
 
     course_id = CourseKeyField(max_length=255, db_index=True)