diff --git a/selftest.py b/selftest.py
index ed2ba815f..f4383b120 100755
--- a/selftest.py
+++ b/selftest.py
@@ -5,7 +5,7 @@ from __future__ import print_function
 import sys
 import os
 
-from PIL import Image, ImageDraw, ImageFilter, ImageMath
+from PIL import Image
 from PIL import features
 
 try:
@@ -26,6 +26,7 @@ def testimage():
     """
     PIL lets you create in-memory images with various pixel types:
 
+    >>> from PIL import Image, ImageDraw, ImageFilter, ImageMath
     >>> im = Image.new("1", (128, 128)) # monochrome
     >>> _info(im)
     (None, '1', (128, 128))
diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index 4a8e37026..c824bf365 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -28,12 +28,15 @@
 # PILLOW_VERSION is deprecated and will be removed after that.
 # Use __version__ instead.
 from . import VERSION, PILLOW_VERSION, __version__, _plugins
+assert VERSION
+assert PILLOW_VERSION
 from ._util import py3
 
 import logging
 import warnings
 import math
 
+
 logger = logging.getLogger(__name__)
 
 
@@ -134,9 +137,8 @@ except ImportError:
 USE_CFFI_ACCESS = hasattr(sys, 'pypy_version_info')
 try:
     import cffi
-    HAS_CFFI = True
 except ImportError:
-    HAS_CFFI = False
+    cffi = None
 
 try:
     from pathlib import Path
@@ -376,26 +378,32 @@ def preinit():
 
     try:
         from . import BmpImagePlugin
+        assert BmpImagePlugin
     except ImportError:
         pass
     try:
         from . import GifImagePlugin
+        assert GifImagePlugin
     except ImportError:
         pass
     try:
         from . import JpegImagePlugin
+        assert JpegImagePlugin
     except ImportError:
         pass
     try:
         from . import PpmImagePlugin
+        assert PpmImagePlugin
     except ImportError:
         pass
     try:
         from . import PngImagePlugin
+        assert PngImagePlugin
     except ImportError:
         pass
 #   try:
 #       import TiffImagePlugin
+#       assert TiffImagePlugin
 #   except ImportError:
 #       pass
 
@@ -833,7 +841,7 @@ class Image(object):
                 self.palette.mode = "RGBA"
 
         if self.im:
-            if HAS_CFFI and USE_CFFI_ACCESS:
+            if cffi and USE_CFFI_ACCESS:
                 if self.pyaccess:
                     return self.pyaccess
                 from . import PyAccess