diff --git a/src/comgate/models.py b/src/comgate/models.py
index ddc5626..6ea345b 100644
--- a/src/comgate/models.py
+++ b/src/comgate/models.py
@@ -121,7 +121,7 @@ class PaymentRequest(BaseModel):
     verification: bool = False
 
     expirationTime: str | None = Field(default=None, pattern=r"^[1-9][0-9]*(m|h|d)$")
-    dynamicExpiration: bool = True
+    dynamicExpiration: bool = False
 
     url_paid: str | None = None
     url_cancelled: str | None = None