diff --git a/DIFFERENCES.md b/DIFFERENCES.md
index d25f6ca..4b51bd7 100644
--- a/DIFFERENCES.md
+++ b/DIFFERENCES.md
@@ -20,6 +20,7 @@ Differences between Mongomallard and Mongoengine
 * `Document.save()` supports `full=True` keyword argument to force saving all model fields.
 * `_get_changed_fields()` / `_changed_fields` returns a set
 * Simplified `EmailField` email regex to be more compatible
+* Assigning invalid types (e.g. an invalid string to `IntField`) raises immediately a `ValueError`
 
 Untested / not implemented yet:
 -----
diff --git a/tests/document/validation.py b/tests/document/validation.py
index b8480a9..4637dee 100644
--- a/tests/document/validation.py
+++ b/tests/document/validation.py
@@ -134,13 +134,8 @@ class ValidatorErrorTest(unittest.TestCase):
         self.assertTrue('e' in keys)
         self.assertTrue('id' in keys)
 
-        doc.e.val = "OK"
-        try:
-            doc.save()
-        except ValidationError, e:
-            self.assertTrue("Doc:test" in e.message)
-            self.assertEqual(e.to_dict(), {
-                "e": {'val': 'OK could not be converted to int'}})
+        with self.assertRaises(ValueError):
+            doc.e.val = "OK"
 
 
 if __name__ == '__main__':
diff --git a/tests/fields/fields.py b/tests/fields/fields.py
index e6a1a37..1eea2ac 100644
--- a/tests/fields/fields.py
+++ b/tests/fields/fields.py
@@ -342,8 +342,8 @@ class FieldTest(unittest.TestCase):
         self.assertRaises(ValidationError, person.validate)
         person.age = 120
         self.assertRaises(ValidationError, person.validate)
-        person.age = 'ten'
-        self.assertRaises(ValidationError, person.validate)
+        with self.assertRaises(ValueError):
+            person.age = 'ten'
 
     def test_float_validation(self):
         """Ensure that invalid values cannot be assigned to float fields.
@@ -871,11 +871,8 @@ class FieldTest(unittest.TestCase):
         e.mapping = [1]
         e.save()
 
-        def create_invalid_mapping():
+        with self.assertRaises(ValueError):
             e.mapping = ["abc"]
-            e.save()
-
-        self.assertRaises(ValidationError, create_invalid_mapping)
 
         Simple.drop_collection()