diff --git a/esphome/core.py b/esphome/core.py
index 52904f0d0b..9b0b8cefa3 100644
--- a/esphome/core.py
+++ b/esphome/core.py
@@ -8,13 +8,16 @@ import os
 import re
 
 # pylint: disable=unused-import, wrong-import-order
-from typing import Any, Dict, List, Optional, Set  # noqa
+from typing import Any, Dict, List, Optional, Set, TYPE_CHECKING  # noqa
 
 from esphome.const import CONF_ARDUINO_VERSION, SOURCE_FILE_EXTENSIONS, \
     CONF_COMMENT, CONF_ESPHOME, CONF_USE_ADDRESS, CONF_WIFI
 from esphome.helpers import ensure_unique_string, is_hassio
 from esphome.util import OrderedDict
 
+if TYPE_CHECKING:
+    from .cpp_generator import MockObj, MockObjClass, Statement
+
 _LOGGER = logging.getLogger(__name__)
 
 
diff --git a/requirements_test.txt b/requirements_test.txt
index 1e1b886923..e8a4f6f1a0 100644
--- a/requirements_test.txt
+++ b/requirements_test.txt
@@ -1,5 +1,5 @@
 pylint==2.5.3
-flake8==3.7.9
+flake8==3.8.3
 pillow
 pexpect