diff --git a/qweechat/buffer.py b/qweechat/buffer.py
index cfe51fc..d4a7ef3 100644
--- a/qweechat/buffer.py
+++ b/qweechat/buffer.py
@@ -131,14 +131,14 @@ class BufferWidget(QtGui.QWidget):
     def set_title(self, title):
         """Set buffer title."""
         self.title.clear()
-        if not title is None:
+        if title is not None:
             self.title.setText(title)
 
     def set_prompt(self, prompt):
         """Set prompt."""
         if self.hbox_edit.count() > 1:
             self.hbox_edit.takeAt(0)
-        if not prompt is None:
+        if prompt is not None:
             label = QtGui.QLabel(prompt)
             label.setContentsMargins(0, 0, 5, 0)
             self.hbox_edit.insertWidget(0, label)
diff --git a/qweechat/weechat/protocol.py b/qweechat/weechat/protocol.py
index 95ddbe4..19d0e13 100644
--- a/qweechat/weechat/protocol.py
+++ b/qweechat/weechat/protocol.py
@@ -55,7 +55,7 @@ class WeechatObject:
         self.separator1 = '\n%s' % self.indent if separator == '\n' else ''
 
     def _str_value(self, v):
-        if type(v) is str and not v is None:
+        if type(v) is str and v is not None:
             return '\'%s\'' % v
         return str(v)