diff --git a/graphene/new_types/field.py b/graphene/new_types/field.py
index f3d998e0..1d5a8259 100644
--- a/graphene/new_types/field.py
+++ b/graphene/new_types/field.py
@@ -61,8 +61,8 @@ class Field(OrderedType):
         self._type = type
         self.args = args or OrderedDict()
         # self.args = to_arguments(args, extra_args)
-        assert not (source and resolver), ('You cannot provide a source and a '
-                                           'resolver in a Field at the same time.')
+        assert not (source and resolver), ('A Field cannot have a source and a '
+                                           'resolver in at the same time.')
         if source:
             resolver = partial(source_resolver, source)
         self.resolver = resolver
diff --git a/graphene/new_types/tests/test_field.py b/graphene/new_types/tests/test_field.py
index 0863f6e4..6ecc9427 100644
--- a/graphene/new_types/tests/test_field.py
+++ b/graphene/new_types/tests/test_field.py
@@ -47,7 +47,7 @@ def test_field_not_source_and_resolver():
     MyType = object()
     with pytest.raises(Exception) as exc_info:
         Field(MyType, source='value', resolver=lambda: None)
-    assert str(exc_info.value) == 'You cannot provide a source and a resolver in a Field at the same time.'
+    assert str(exc_info.value) == 'A Field cannot have a source and a resolver in at the same time.'
 
 def test_field_source_func():
     MyType = object()