diff --git a/InvenTree/common/models.py b/InvenTree/common/models.py
index f08aad1c68..7d4b69f7a6 100644
--- a/InvenTree/common/models.py
+++ b/InvenTree/common/models.py
@@ -726,7 +726,7 @@ class PriceBreak(models.Model):
         return converted.amount
 
 
-def get_price(instance, quantity, moq=True, multiples=True, currency=None, break_name:str='price_breaks'):
+def get_price(instance, quantity, moq=True, multiples=True, currency=None, break_name: str = 'price_breaks'):
     """ Calculate the price based on quantity price breaks.
 
     - Don't forget to add in flat-fee cost (base_cost field)
diff --git a/InvenTree/part/models.py b/InvenTree/part/models.py
index 9ff4938891..7133048527 100644
--- a/InvenTree/part/models.py
+++ b/InvenTree/part/models.py
@@ -1649,8 +1649,8 @@ class Part(MPTTModel):
             price=price
         )
 
-    def get_internal_price(instance, quantity, moq=True, multiples=True, currency=None):
-        return common.models.get_price(instance, quantity, moq, multiples, currency, break_name='internal_price_breaks')
+    def get_internal_price(self, quantity, moq=True, multiples=True, currency=None):
+        return common.models.get_price(self, quantity, moq, multiples, currency, break_name='internal_price_breaks')
 
     @property
     def has_internal_price_breaks(self):