diff --git a/pricing/pricing.py b/pricing/pricing.py
index 25817d1..805bf6e 100644
--- a/pricing/pricing.py
+++ b/pricing/pricing.py
@@ -354,7 +354,7 @@ where a.id = b.ppid
 			times = 1
 			unit = 1
 			for k,spec_value in p.items():
-				if k == 'price':
+				if k in ['price', 'formula']:
 					continue
 				f = d.fields.get(k)
 				if not f:
@@ -384,6 +384,7 @@ where a.id = b.ppid
 				np = p.copy()
 				times = float(times)
 				unit = float(unit)
+				formula = p.formula or d.formula
 				if formula:
 					ns = {
 						'price': p.price,