diff --git a/userapi/storage/postgres/accounts_table.go b/userapi/storage/postgres/accounts_table.go
index 268889ac..e3cab56e 100644
--- a/userapi/storage/postgres/accounts_table.go
+++ b/userapi/storage/postgres/accounts_table.go
@@ -65,7 +65,7 @@ const selectPasswordHashSQL = "" +
 	"SELECT password_hash FROM account_accounts WHERE localpart = $1 AND is_deactivated = FALSE"
 
 const selectNewNumericLocalpartSQL = "" +
-	"SELECT COALESCE(MAX(localpart::integer), 0) FROM account_accounts WHERE localpart ~ '^[0-9]{1,}$'"
+	"SELECT COALESCE(MAX(localpart::bigint), 0) FROM account_accounts WHERE localpart ~ '^[0-9]{1,}$'"
 
 type accountsStatements struct {
 	insertAccountStmt             *sql.Stmt
diff --git a/userapi/storage/storage_test.go b/userapi/storage/storage_test.go
index 66c15454..a2609733 100644
--- a/userapi/storage/storage_test.go
+++ b/userapi/storage/storage_test.go
@@ -133,6 +133,14 @@ func Test_Accounts(t *testing.T) {
 		// test getting a numeric localpart, with an existing user without a localpart
 		_, err = db.CreateAccount(ctx, "", "", "", api.AccountTypeGuest)
 		assert.NoError(t, err)
+
+		// Create a user with a high numeric localpart, out of range for the Postgres integer (2147483647) type
+		_, err = db.CreateAccount(ctx, "2147483650", "", "", api.AccountTypeUser)
+		assert.NoError(t, err)
+
+		// Now try to create a new guest user
+		_, err = db.CreateAccount(ctx, "", "", "", api.AccountTypeGuest)
+		assert.NoError(t, err)
 	})
 }