diff --git a/federationsender/storage/postgres/joined_hosts_table.go b/federationsender/storage/postgres/joined_hosts_table.go
index cc112b7f3..fab9b427d 100644
--- a/federationsender/storage/postgres/joined_hosts_table.go
+++ b/federationsender/storage/postgres/joined_hosts_table.go
@@ -48,7 +48,8 @@ CREATE INDEX IF NOT EXISTS federatonsender_joined_hosts_room_id_idx
 
 const insertJoinedHostsSQL = "" +
 	"INSERT INTO federationsender_joined_hosts (room_id, event_id, server_name)" +
-	" VALUES ($1, $2, $3)"
+	" VALUES ($1, $2, $3)" +
+	" ON CONFLICT DO NOTHING"
 
 const deleteJoinedHostsSQL = "" +
 	"DELETE FROM federationsender_joined_hosts WHERE event_id = ANY($1)"
diff --git a/federationsender/storage/sqlite3/joined_hosts_table.go b/federationsender/storage/sqlite3/joined_hosts_table.go
index 3bc45e7d5..01e4650e0 100644
--- a/federationsender/storage/sqlite3/joined_hosts_table.go
+++ b/federationsender/storage/sqlite3/joined_hosts_table.go
@@ -47,7 +47,7 @@ CREATE INDEX IF NOT EXISTS federatonsender_joined_hosts_room_id_idx
 `
 
 const insertJoinedHostsSQL = "" +
-	"INSERT INTO federationsender_joined_hosts (room_id, event_id, server_name)" +
+	"INSERT OR IGNORE INTO federationsender_joined_hosts (room_id, event_id, server_name)" +
 	" VALUES ($1, $2, $3)"
 
 const deleteJoinedHostsSQL = "" +