diff --git a/copanier/models.py b/copanier/models.py
index bdb5f36..910b23e 100644
--- a/copanier/models.py
+++ b/copanier/models.py
@@ -134,9 +134,12 @@ class Order(Base):
 
     def total(self, products):
         products = {p.ref: p for p in products}
-        return round(
-            sum(p.quantity * products[ref].price for ref, p in self.products.items()), 2
+        total = sum(
+            p.quantity * products[ref].price
+            for ref, p in self.products.items()
+            if ref in products
         )
+        return round(total, 2)
 
     @property
     def has_adjustments(self):
diff --git a/tests/test_models.py b/tests/test_models.py
index 4cc531d..7bae88f 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -105,6 +105,16 @@ def test_order_has_adjustments():
     assert order.has_adjustments
 
 
+def test_order_total(delivery):
+    delivery.products = [Product(name="Lait", ref="123", price=1.5)]
+    order = Order()
+    assert order.total(delivery.products) == 0
+    order.products["123"] = ProductOrder(wanted=2)
+    assert order.total(delivery.products) == 3
+    order.products["unknown"] = ProductOrder(wanted=2)
+    assert order.total(delivery.products) == 3
+
+
 def test_can_persist_delivery(delivery):
     with pytest.raises(AssertionError):
         delivery.path