diff --git a/lms/djangoapps/courseware/migrations/0003_done_grade_cache.py b/lms/djangoapps/courseware/migrations/0003_done_grade_cache.py
index f29f931079..0ab35551c9 100644
--- a/lms/djangoapps/courseware/migrations/0003_done_grade_cache.py
+++ b/lms/djangoapps/courseware/migrations/0003_done_grade_cache.py
@@ -10,7 +10,7 @@ class Migration(SchemaMigration):
     def forwards(self, orm):
 
         # NOTE (vshnayder): This constraint has the wrong field order, so it doesn't actually
-        # do anything.  Migration 0004 actually removes this index.
+        # do anything in sqlite.  Migration 0004 actually removes this index for sqlite.
         # Removing unique constraint on 'StudentModule', fields ['module_id', 'module_type', 'student']
         db.delete_unique('courseware_studentmodule', ['module_id', 'module_type', 'student_id'])
 
diff --git a/lms/djangoapps/courseware/migrations/0004_add_field_studentmodule_course_id.py b/lms/djangoapps/courseware/migrations/0004_add_field_studentmodule_course_id.py
index 7433a48b0b..ff79901824 100644
--- a/lms/djangoapps/courseware/migrations/0004_add_field_studentmodule_course_id.py
+++ b/lms/djangoapps/courseware/migrations/0004_add_field_studentmodule_course_id.py
@@ -16,9 +16,10 @@ class Migration(SchemaMigration):
         # Removing unique constraint on 'StudentModule', fields ['module_id', 'student']
         db.delete_unique('courseware_studentmodule', ['module_id', 'student_id'])
 
-        # NOTE: manually remove this constaint (from 0001)--0003 tries, but fails.
+        # NOTE: manually remove this constaint (from 0001)--0003 tries, but fails for sqlite.
         # Removing unique constraint on 'StudentModule', fields ['module_id', 'module_type', 'student']
-        db.delete_unique('courseware_studentmodule', ['student_id', 'module_id', 'module_type'])
+        if db.backend_name == "sqlite3":
+            db.delete_unique('courseware_studentmodule', ['student_id', 'module_id', 'module_type'])
 
         # Adding unique constraint on 'StudentModule', fields ['course_id', 'module_state_key', 'student']
         db.create_unique('courseware_studentmodule', ['student_id', 'module_id', 'course_id'])