diff --git a/lib/policy/decision.ts b/lib/policy/decision.ts
index 5b55296..cf9039d 100644
--- a/lib/policy/decision.ts
+++ b/lib/policy/decision.ts
@@ -9,6 +9,7 @@ export type ReasonCode =
   | "PAYMENT_FAILED"
   | "IDEMPOTENT_NOOP"
   | "VALIDATION_FAILED"
+  | "DUPLICATE_REQUEST"
 
 export interface PolicyDecision {
   ok: boolean