diff --git a/barker/barker/schemas/voucher.py b/barker/barker/schemas/voucher.py
index 07b9dff..6ef4cf3 100644
--- a/barker/barker/schemas/voucher.py
+++ b/barker/barker/schemas/voucher.py
@@ -55,11 +55,9 @@ class Inventory(BaseModel):
 
     @model_validator(mode="after")
     def calculate_amount(self) -> "Inventory":
+        price = 0 if self.is_happy_hour else self.price
         self.amount = round(
-            Decimal(
-                (self.price or Decimal(0)) * self.quantity * (1 - self.discount) * (1 + (self.tax_rate or Decimal(0)))
-            ),
-            2,
+            Decimal(price * self.quantity * (1 - self.discount) * (1 + (self.tax_rate or Decimal(0)))), 2
         )
         return self