diff --git a/openapi_core/unmarshalling/schemas/factories.py b/openapi_core/unmarshalling/schemas/factories.py
index 660affb..60f90dc 100644
--- a/openapi_core/unmarshalling/schemas/factories.py
+++ b/openapi_core/unmarshalling/schemas/factories.py
@@ -1,7 +1,6 @@
-from copy import copy
 import warnings
 
-from openapi_schema_validator import OAS30Validator, oas30_format_checker
+from openapi_schema_validator import OAS30Validator
 
 from openapi_core.schema.schemas.enums import SchemaType, SchemaFormat
 from openapi_core.schema.schemas.models import Schema
@@ -35,8 +34,11 @@ class SchemaUnmarshallersFactory(object):
         UnmarshalContext.RESPONSE: 'read',
     }
 
-    def __init__(self, resolver=None, custom_formatters=None, context=None):
+    def __init__(
+            self, resolver=None, format_checker=None,
+            custom_formatters=None, context=None):
         self.resolver = resolver
+        self.format_checker = format_checker
         if custom_formatters is None:
             custom_formatters = {}
         self.custom_formatters = custom_formatters
@@ -79,17 +81,10 @@ class SchemaUnmarshallersFactory(object):
             return default_formatters.get(schema_format)
 
     def get_validator(self, schema):
-        format_checker = self._get_format_checker()
         kwargs = {
             'resolver': self.resolver,
-            'format_checker': format_checker,
+            'format_checker': self.format_checker,
         }
         if self.context is not None:
             kwargs[self.CONTEXT_VALIDATION[self.context]] = True
         return OAS30Validator(schema.__dict__, **kwargs)
-
-    def _get_format_checker(self):
-        fc = copy(oas30_format_checker)
-        for name, formatter in self.custom_formatters.items():
-            fc.checks(name)(formatter.validate)
-        return fc
diff --git a/openapi_core/unmarshalling/schemas/util.py b/openapi_core/unmarshalling/schemas/util.py
index d5ac76c..66654ca 100644
--- a/openapi_core/unmarshalling/schemas/util.py
+++ b/openapi_core/unmarshalling/schemas/util.py
@@ -1,10 +1,15 @@
 """OpenAPI core schemas util module"""
 from base64 import b64decode
+from copy import copy
 import datetime
 from distutils.util import strtobool
 from six import string_types, text_type, integer_types
 from uuid import UUID
 
+from openapi_schema_validator import oas30_format_checker
+
+from openapi_core.compat import lru_cache
+
 
 def forcebool(val):
     if isinstance(val, string_types):
@@ -32,3 +37,14 @@ def format_number(value):
         return value
 
     return float(value)
+
+
+@lru_cache()
+def build_format_checker(**custom_formatters):
+    if not custom_formatters:
+        return oas30_format_checker
+
+    fc = copy(oas30_format_checker)
+    for name, formatter in custom_formatters.items():
+        fc.checks(name)(formatter.validate)
+    return fc
diff --git a/openapi_core/validation/validators.py b/openapi_core/validation/validators.py
index 271209c..4d3639c 100644
--- a/openapi_core/validation/validators.py
+++ b/openapi_core/validation/validators.py
@@ -1,4 +1,5 @@
 """OpenAPI core validation validators module"""
+from openapi_core.unmarshalling.schemas.util import build_format_checker
 
 
 class BaseValidator(object):
@@ -10,9 +11,11 @@ class BaseValidator(object):
     ):
         self.spec = spec
         self.base_url = base_url
-        self.custom_formatters = custom_formatters
+        self.custom_formatters = custom_formatters or {}
         self.custom_media_type_deserializers = custom_media_type_deserializers
 
+        self.format_checker = build_format_checker(**self.custom_formatters)
+
     def _find_path(self, request):
         from openapi_core.templating.paths.finders import PathFinder
         finder = PathFinder(self.spec, base_url=self.base_url)
@@ -45,8 +48,8 @@ class BaseValidator(object):
             SchemaUnmarshallersFactory,
         )
         unmarshallers_factory = SchemaUnmarshallersFactory(
-            self.spec._resolver, self.custom_formatters,
-            context=context,
+            self.spec._resolver, self.format_checker,
+            self.custom_formatters, context=context,
         )
         unmarshaller = unmarshallers_factory.create(
             param_or_media_type.schema)
diff --git a/tests/unit/unmarshalling/test_unmarshal.py b/tests/unit/unmarshalling/test_unmarshal.py
index 72033fd..1c7e145 100644
--- a/tests/unit/unmarshalling/test_unmarshal.py
+++ b/tests/unit/unmarshalling/test_unmarshal.py
@@ -18,12 +18,16 @@ from openapi_core.unmarshalling.schemas.factories import (
     SchemaUnmarshallersFactory,
 )
 from openapi_core.unmarshalling.schemas.formatters import Formatter
+from openapi_core.unmarshalling.schemas.util import build_format_checker
 
 
 @pytest.fixture
 def unmarshaller_factory():
     def create_unmarshaller(schema, custom_formatters=None, context=None):
+        custom_formatters = custom_formatters or {}
+        format_checker = build_format_checker(**custom_formatters)
         return SchemaUnmarshallersFactory(
+            format_checker=format_checker,
             custom_formatters=custom_formatters, context=context).create(
                 schema)
     return create_unmarshaller
diff --git a/tests/unit/unmarshalling/test_validate.py b/tests/unit/unmarshalling/test_validate.py
index fdb5d95..6c91ce3 100644
--- a/tests/unit/unmarshalling/test_validate.py
+++ b/tests/unit/unmarshalling/test_validate.py
@@ -12,6 +12,7 @@ from openapi_core.unmarshalling.schemas.factories import (
 from openapi_core.unmarshalling.schemas.exceptions import (
     FormatterNotFoundError, InvalidSchemaValue,
 )
+from openapi_core.unmarshalling.schemas.util import build_format_checker
 
 from six import b, u
 
@@ -21,7 +22,9 @@ class TestSchemaValidate(object):
     @pytest.fixture
     def validator_factory(self):
         def create_validator(schema):
-            return SchemaUnmarshallersFactory().create(schema)
+            format_checker = build_format_checker()
+            return SchemaUnmarshallersFactory(
+                format_checker=format_checker).create(schema)
         return create_validator
 
     @pytest.mark.parametrize('schema_type', [