55P04ERRORTier 2 — Caution✅ HIGH confidence

unsafe use of new enum value

Category: Object Not in Prerequisite StateVersions: Postgres 9.1+

What this means

SQLSTATE 55P04 is raised when a newly added enum value (via ALTER TYPE ... ADD VALUE) is used in a query within the same transaction that added it. Postgres cannot safely use a new enum value until the transaction that added it commits.

Why it happens

1Using a new enum label in the same transaction that added it with ALTER TYPE ... ADD VALUE

How to reproduce

Using a new enum value in the same transaction that added it.

trigger — this will ERROR

BEGIN;
ALTER TYPE status_enum ADD VALUE 'archived';
INSERT INTO orders (status) VALUES ('archived'); -- 55P04: value not committed yet
COMMIT;

ERROR: unsafe use of new value "archived" of enum type status_enum HINT: New enum values must be committed before they can be used.

Fix 1: Commit the ALTER TYPE in a separate transaction before using the new value

When adding a new enum value and then using it.

fix

-- Transaction 1:
ALTER TYPE status_enum ADD VALUE 'archived';
-- COMMIT;

-- Transaction 2 (after COMMIT):
INSERT INTO orders (status) VALUES ('archived');

Why this works

The new enum value is not visible to catalog lookups until the adding transaction commits. Using it in two separate transactions resolves the ordering dependency.

Version notes

Postgres 9.1+ALTER TYPE ... ADD VALUE introduced in Postgres 9.1. The same-transaction restriction has applied since then.

Sources

📚 Official docs: https://www.postgresql.org/docs/current/errcodes-appendix.html

🔧 Source ref: Class 55 — Object Not in Prerequisite State (Postgres-specific)

Confidence assessment

✅ HIGH confidence

Postgres-specific. Stable since 9.1. A common migration pitfall.