diff --git a/bom.py b/bom.py
index 9719a89d7d..056841848e 100644
--- a/bom.py
+++ b/bom.py
@@ -89,8 +89,8 @@ class BOMInput(ModelSQL, ModelView):
     @fields.depends('product', 'uom')
     def on_change_product(self):
         if self.product:
-            uoms = self.product.default_uom.category.uoms
-            if (not self.uom or self.uom not in uoms):
+            category = self.product.default_uom.category
+            if not self.uom or self.uom.category != category:
                 self.uom = self.product.default_uom
                 self.unit_digits = self.product.default_uom.digits
         else:
diff --git a/production.py b/production.py
index 390f325b16..dfb92f41bd 100644
--- a/production.py
+++ b/production.py
@@ -346,8 +346,8 @@ class Production(Workflow, ModelSQL, ModelView):
     @fields.depends(*BOM_CHANGES)
     def on_change_product(self):
         if self.product:
-            uoms = self.product.default_uom.category.uoms
-            if (not self.uom or self.uom not in uoms):
+            category = self.product.default_uom.category
+            if not self.uom or self.uom.category != category:
                 self.uom = self.product.default_uom
                 self.unit_digits = self.product.default_uom.digits
         else: