diff --git a/roomserver/storage/sqlite3/deltas/2021041615092700_state_blocks_refactor.go b/roomserver/storage/sqlite3/deltas/2021041615092700_state_blocks_refactor.go
index 42edbbc6f..0cf1f733a 100644
--- a/roomserver/storage/sqlite3/deltas/2021041615092700_state_blocks_refactor.go
+++ b/roomserver/storage/sqlite3/deltas/2021041615092700_state_blocks_refactor.go
@@ -93,6 +93,20 @@ func UpStateBlocksRefactor(tx *sql.Tx) error {
 		}
 
 		var newblocks types.StateBlockNIDs
+		if len(blocks) == 0 {
+			// some m.room.create events have a state snapshot but no state blocks at all which makes
+			// sense as there is no state before creation. The correct form should be to give the event
+			// in question a state snapshot NID of 0 to indicate 'no snapshot'.
+			// If we don't do this, we'll fail the assertions later on which try to ensure we didn't forget
+			// any snapshots.
+			_, err = tx.Exec(
+				`UPDATE roomserver_events SET state_snapshot_nid = 0 WHERE event_type_nid = $1 AND state_snapshot_nid = $2`,
+				types.MRoomCreateNID, snapshot,
+			)
+			if err != nil {
+				return fmt.Errorf("resetting create events snapshots to 0 errored: %s", err)
+			}
+		}
 		for _, block := range blocks {
 			if err = func() error {
 				blockrows, berr := tx.Query(`SELECT event_nid FROM _roomserver_state_block WHERE state_block_nid = $1`, block)