diff --git a/19.md b/19.md
index 1196658f..cf76f8b1 100644
--- a/19.md
+++ b/19.md
@@ -154,7 +154,7 @@ Response of `Bob`:
 }
 ```
 
-If the invoice was not paid yet, `Bob` responds with an error. In that case, `Alice` **CAN** repeat the same request until the Lightning invoice is settled, as in NUT04. If `Alice` does not include a witness on the `PostMintBolt11Request` but did include a `pubkey` in the `PostMintBolt11QuoteRequest` the `Bob` **MUST** respond with an error, `Alice` **CAN** repeat the request with a witness in order to mint the ecash.
+If the invoice was not paid yet, `Bob` responds with an error. In that case, `Alice` **MAY** repeat the same request until the Lightning invoice is settled, as in NUT04. If `Alice` does not include a witness on the `PostMintBolt11Request` but did include a `pubkey` in the `PostMintBolt11QuoteRequest` then `Bob` **MUST** respond with an error, `Alice` **SHOULD** repeat the request with a witness in order to mint the ecash.
 
 ## Settings