diff --git a/plan.py b/plan.py
index 4471fdf..ea7ae7c 100644
--- a/plan.py
+++ b/plan.py
@@ -150,7 +150,7 @@ class Plan(ModelSQL, ModelView):
             if input_.product.boms:
                 product_bom = input_.product.boms[0].bom
                 res.append((input_.product.id, product_bom.id))
-                if product_bom.id not in (x[1] for x in res if x):
+                if product_bom.id not in (x[1] for x in res):
                     res += self.find_boms(product_bom.inputs)
         return res