diff --git a/HISTORY.rst b/HISTORY.rst
index e1940d1..02575b2 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -6,6 +6,7 @@ History
 v0.19.0 (unreleased)
 ....................
 * Support ``Callable`` type hint, fix #279 by @proofit404
+* Fix schema for fields with ``validator`` decorator, fix #375 by @tiangolo
 
 v0.18.2 (2019-01-22)
 ....................
diff --git a/pydantic/fields.py b/pydantic/fields.py
index 42604f8..a944ebe 100644
--- a/pydantic/fields.py
+++ b/pydantic/fields.py
@@ -7,7 +7,7 @@ from .class_validators import Validator, ValidatorSignature, get_validator_signa
 from .error_wrappers import ErrorWrapper
 from .types import Json, JsonWrapper
 from .utils import Callable, ForwardRef, display_as_type, lenient_issubclass, list_like
-from .validators import NoneType, dict_validator, find_validators, is_none_validator
+from .validators import NoneType, dict_validator, find_validators
 
 Required: Any = Ellipsis
 
@@ -358,7 +358,7 @@ class Field:
         """
         False if this is a simple field just allowing None as used in Unions/Optional.
         """
-        return len(self.validators) != 1 or self.validators[0][1] != is_none_validator
+        return self.type_ != NoneType
 
     def is_complex(self):
         """
diff --git a/tests/test_schema.py b/tests/test_schema.py
index ff6b6c1..861e1d4 100644
--- a/tests/test_schema.py
+++ b/tests/test_schema.py
@@ -10,7 +10,7 @@ from uuid import UUID
 
 import pytest
 
-from pydantic import BaseModel, Schema, ValidationError
+from pydantic import BaseModel, Schema, ValidationError, validator
 from pydantic.schema import get_flat_models_from_model, get_flat_models_from_models, get_model_name_map, schema
 from pydantic.types import (
     DSN,
@@ -1104,3 +1104,18 @@ def test_optional_dict():
 
     assert Model().dict() == {'something': None}
     assert Model(something={'foo': 'Bar'}).dict() == {'something': {'foo': 'Bar'}}
+
+
+def test_field_with_validator():
+    class Model(BaseModel):
+        something: Optional[int] = None
+
+        @validator('something')
+        def check_field(cls, v, *, values, config, field):
+            return v
+
+    assert Model.schema() == {
+        'title': 'Model',
+        'type': 'object',
+        'properties': {'something': {'type': 'integer', 'title': 'Something'}},
+    }