diff --git a/synapse/storage/schema/delta/32/reports.sql b/synapse/storage/schema/delta/32/reports.sql
index 3f2502745..d13609776 100644
--- a/synapse/storage/schema/delta/32/reports.sql
+++ b/synapse/storage/schema/delta/32/reports.sql
@@ -15,7 +15,7 @@
 
 
 CREATE TABLE event_reports(
-    id BIGINT NOT NULL,
+    id BIGINT NOT NULL PRIMARY KEY,
     received_ts BIGINT NOT NULL,
     room_id TEXT NOT NULL,
     event_id TEXT NOT NULL,