diff --git a/src/PIL/ImageQt.py b/src/PIL/ImageQt.py
index bdfe3886c..b747781c5 100644
--- a/src/PIL/ImageQt.py
+++ b/src/PIL/ImageQt.py
@@ -140,7 +140,7 @@ def _toqclass_helper(im):
         if py3:
             im = str(im.toUtf8(), "utf-8")
         else:
-            im = unicode(im.toUtf8(), "utf-8")
+            im = unicode(im.toUtf8(), "utf-8")  # noqa: F821
     if isPath(im):
         im = Image.open(im)
 
diff --git a/src/PIL/PdfParser.py b/src/PIL/PdfParser.py
index 66d6ecfb1..7216e5b95 100644
--- a/src/PIL/PdfParser.py
+++ b/src/PIL/PdfParser.py
@@ -373,7 +373,7 @@ def pdf_repr(x):
     elif isinstance(x, list):
         return bytes(PdfArray(x))
     elif ((py3 and isinstance(x, str)) or
-          (not py3 and isinstance(x, unicode))):
+          (not py3 and isinstance(x, unicode))):  # noqa: F821
         return pdf_repr(encode_text(x))
     elif isinstance(x, bytes):
         # XXX escape more chars? handle binary garbage
diff --git a/src/PIL/TiffImagePlugin.py b/src/PIL/TiffImagePlugin.py
index 7859de531..30d5e620e 100644
--- a/src/PIL/TiffImagePlugin.py
+++ b/src/PIL/TiffImagePlugin.py
@@ -541,7 +541,7 @@ class ImageFileDirectory_v2(MutableMapping):
     def _setitem(self, tag, value, legacy_api):
         basetypes = (Number, bytes, str)
         if not py3:
-            basetypes += unicode,
+            basetypes += unicode,  # noqa: F821
 
         info = TiffTags.lookup(tag)
         values = [value] if isinstance(value, basetypes) else value
@@ -623,13 +623,13 @@ class ImageFileDirectory_v2(MutableMapping):
             from .TiffTags import TYPES
             if func.__name__.startswith("load_"):
                 TYPES[idx] = func.__name__[5:].replace("_", " ")
-            _load_dispatch[idx] = size, func
+            _load_dispatch[idx] = size, func  # noqa: F821
             return func
         return decorator
 
     def _register_writer(idx):
         def decorator(func):
-            _write_dispatch[idx] = func
+            _write_dispatch[idx] = func  # noqa: F821
             return func
         return decorator
 
@@ -638,9 +638,9 @@ class ImageFileDirectory_v2(MutableMapping):
         idx, fmt, name = idx_fmt_name
         TYPES[idx] = name
         size = struct.calcsize("=" + fmt)
-        _load_dispatch[idx] = size, lambda self, data, legacy_api=True: (
+        _load_dispatch[idx] = size, lambda self, data, legacy_api=True: (  # noqa: F821
             self._unpack("{}{}".format(len(data) // size, fmt), data))
-        _write_dispatch[idx] = lambda self, *values: (
+        _write_dispatch[idx] = lambda self, *values: (  # noqa: F821
             b"".join(self._pack(fmt, value) for value in values))
 
     list(map(_register_basic,
@@ -1507,7 +1507,7 @@ def _save(im, fp, filename):
             if tag not in TiffTags.LIBTIFF_CORE:
                 continue
             if tag not in atts and tag not in blocklist:
-                if isinstance(value, str if py3 else unicode):
+                if isinstance(value, str if py3 else unicode):  # noqa: F821
                     atts[tag] = value.encode('ascii', 'replace') + b"\0"
                 elif isinstance(value, IFDRational):
                     atts[tag] = float(value)
diff --git a/src/PIL/_util.py b/src/PIL/_util.py
index e6989d69d..5828c2c24 100644
--- a/src/PIL/_util.py
+++ b/src/PIL/_util.py
@@ -11,10 +11,10 @@ if py3:
         return isinstance(f, (bytes, str))
 else:
     def isStringType(t):
-        return isinstance(t, basestring)
+        return isinstance(t, basestring)  # noqa: F821
 
     def isPath(f):
-        return isinstance(f, basestring)
+        return isinstance(f, basestring)  # noqa: F821
 
 
 # Checks if an object is a string, and that it points to a directory.