diff --git a/alembic/versions/16b2bee7db72_backfill_signature_summary_os_28_days.py b/alembic/versions/16b2bee7db72_backfill_signature_summary_os_28_days.py
new file mode 100644
index 0000000000..895d3162c4
--- /dev/null
+++ b/alembic/versions/16b2bee7db72_backfill_signature_summary_os_28_days.py
@@ -0,0 +1,47 @@
+"""backfill signature_summary_os 28 days
+
+Revision ID: 16b2bee7db72
+Revises: 4afd4e13281d
+Create Date: 2015-09-02 13:53:13.505082
+
+"""
+import datetime
+
+# revision identifiers, used by Alembic.
+revision = '16b2bee7db72'
+down_revision = '4afd4e13281d'
+
+from alembic import op
+
+
+def upgrade():
+    # We only ever, at most, show 28 days in the report list that
+    # shows this signature summary.
+    today = datetime.datetime.utcnow().date()
+    for i in range(28, 0, -1):
+        then = today - datetime.timedelta(days=i)
+        till = then + datetime.timedelta(days=1)
+        op.execute(
+            """
+            SELECT
+                backfill_weekly_report_partitions(
+                    '%s', '%s', 'signature_summary_os'
+                )
+            """ % (
+                then.strftime('%Y-%m-%d'),
+                till.strftime('%Y-%m-%d')
+            )
+        )
+        op.execute(
+            """
+            SELECT
+                update_signature_summary_os('%s')
+            """ % (
+                then.strftime('%Y-%m-%d'),
+            )
+        )
+        op.execute('COMMIT')
+
+
+def downgrade():
+    pass