diff --git a/sloth/core/labeltool.py b/sloth/core/labeltool.py
index df758c8..9c231b7 100755
--- a/sloth/core/labeltool.py
+++ b/sloth/core/labeltool.py
@@ -287,7 +287,7 @@ class LabelTool(QObject):
 
         current = self._current_image
         if current is None:
-            current = self._model.iterator(ImageModelItem).next()
+            current = next(self._model.iterator(ImageModelItem))
 
         next_image = current.getSibling(idx)
         if next_image is not None:
@@ -298,7 +298,7 @@ class LabelTool(QObject):
             if self._current_image is not None:
                 next_image = self._current_image.getNextSibling(step)
             else:
-                next_image = self._model.iterator(ImageModelItem).next()
+                next_image = next(self._model.iterator(ImageModelItem))
                 if next_image is not None:
                     next_image = next_image.getNextSibling(step-1)
 
diff --git a/sloth/gui/labeltool.py b/sloth/gui/labeltool.py
index b1a0793..90caa31 100755
--- a/sloth/gui/labeltool.py
+++ b/sloth/gui/labeltool.py
@@ -48,10 +48,7 @@ class BackgroundLoader(QObject):
             self._message_displayed = True
         if self._level <= self._max_levels and self._rows > 0:
             try:
-                if hasattr(self._iterator, "next"):
-                    item = self._iterator.next()
-                else:
-                    item = next(self._iterator)
+                item = next(self._iterator)
                 self._next_rows += item.rowCount()
                 self._pos += 1
                 self._progress.setValue(int((float(self._pos) / float(self._rows) + self._level - 1) * 1000))
diff --git a/sloth/gui/propertyeditor.py b/sloth/gui/propertyeditor.py
index 56e0f83..482c781 100644
--- a/sloth/gui/propertyeditor.py
+++ b/sloth/gui/propertyeditor.py
@@ -179,11 +179,7 @@ class DefaultAttributeHandler(QGroupBox, AbstractAttributeHandler):
                 self._inputField.setPlaceholderText(", ".join(selected_values))
             elif len(selected_values) == 1:
                 it = iter(selected_values)
-                if hasattr(it, 'next'):
-                    self._inputField.setText(it.next())
-                else:
-                    self._inputField.setText(next(it))
-
+                self._inputField.setText(next(it))
 
     def updateButtons(self):
         selected_values = self.getSelectedValues()