diff --git a/BTCPayServer/wwwroot/swagger/v1/swagger.template.invoices.json b/BTCPayServer/wwwroot/swagger/v1/swagger.template.invoices.json
index 1c870c31e..4a496c3a4 100644
--- a/BTCPayServer/wwwroot/swagger/v1/swagger.template.invoices.json
+++ b/BTCPayServer/wwwroot/swagger/v1/swagger.template.invoices.json
@@ -737,7 +737,7 @@
                             "amount": {
                                 "type": "string",
                                 "format": "decimal",
-                                "description": "The amount of the invoice",
+                                "description": "The amount of the invoice. Note that the amount will be zero for a top-up invoice that is paid after invoice expiry.",
                                 "example": "5.00"
                             },
                             "currency": {