diff --git a/server/core_storage.go b/server/core_storage.go
index 3240318cd21ea1263a7017aee19c81ef70d8bedd..b5e9a62c9672d9e556dc3b54fd34cb9e152e69f0 100644
--- a/server/core_storage.go
+++ b/server/core_storage.go
@@ -699,6 +699,7 @@ func storagePrepBatch(batch *pgx.Batch, authoritativeWrite bool, op *StorageOpWr
 		query = `
 		INSERT INTO storage (collection, key, user_id, value, version, read, write, create_time, update_time)
 		VALUES ($1, $2, $3, $4, $5, $6, $7, now(), now())
+		ON CONFLICT (collection, key, user_id) DO NOTHING 
 		RETURNING read, write, version, create_time, update_time`
 
 		// Outcomes: