diff --git a/plugins/python/mixer_slider_docker/mixer_slider_docker.py b/plugins/python/mixer_slider_docker/mixer_slider_docker.py
index a5d227ec20..ef92fb42be 100644
--- a/plugins/python/mixer_slider_docker/mixer_slider_docker.py
+++ b/plugins/python/mixer_slider_docker/mixer_slider_docker.py
@@ -1,128 +1,130 @@
 '''
     Copyright (C) 2019 Tusooa Zhu <tusooa@vista.aero>
 
     This file is part of Krita-docker-color-slider.
 
     Krita-docker-color-slider is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation, either version 3 of the License, or
     (at your option) any later version.
 
     Krita-docker-color-slider is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
 
     You should have received a copy of the GNU General Public License
     along with Krita-docker-color-slider.  If not, see <https://www.gnu.org/licenses/>.
 '''
 from PyQt5.QtGui import QColor
 from PyQt5.QtWidgets import QWidget, QVBoxLayout, QHBoxLayout, QPushButton
 
 from krita import Krita, DockWidget, ManagedColor, DockWidgetFactory, DockWidgetFactoryBase
 
 from .slider_line import SliderLine
 from .ui_mixer_slider_docker import UIMixerSliderDocker
 
 
 class MixerSliderDocker(DockWidget):
     # Init the docker
 
     def __init__(self):
         super(MixerSliderDocker, self).__init__()
 
         main_program = Krita.instance()
         settings = main_program.readSetting("", "MixerSliderColors",
                                             "RGBA,U8,sRGB-elle-V2-srgbtrc.icc,1,0.8,0.4,1|" +
                                             "RGBA,U8,sRGB-elle-V2-srgbtrc.icc,0,0,0,1")  # alpha=1 == non-transparent
 
         self.default_left_color = self.qcolor_to_managedcolor(QColor.fromRgbF(0.4, 0.8, 1, 1))
         self.default_right_color = self.qcolor_to_managedcolor(QColor.fromRgbF(0, 0, 0, 1))
 
         # make base-widget and layout
         self.widget = QWidget()
         self.sliders = []
         self.top_layout = QVBoxLayout()
         self.main_layout = QHBoxLayout()
         self.top_layout.addLayout(self.main_layout)
         self.top_layout.addStretch(0)
         # The text on the button for settings
         self.settings_button = QPushButton(i18n('S'))
         self.settings_button.setToolTip(i18n('Change settings'))
         self.settings_button.setMaximumSize(30, 30)
         self.main_layout.addWidget(self.settings_button)
         self.layout = QVBoxLayout()
         self.layout.setSpacing(0)
         self.main_layout.addLayout(self.layout)
         for line in settings.split(";"):
             colors = line.split('|')
+            if len(colors) < 2:  # discard old configurations
+                continue
             left_color = self.parse_color(colors[0].split(','))
             right_color = self.parse_color(colors[1].split(','))
             widget = SliderLine(left_color, right_color, self)
             self.sliders.append(widget)
             self.layout.addWidget(widget)
 
         self.widget.setLayout(self.top_layout)
         self.setWindowTitle(i18n("Mixer Slider Docker"))
         self.setWidget(self.widget)
         [x.show() for x in self.sliders]
 
         self.settings_button.clicked.connect(self.init_ui)
 
     def settings_changed(self):
         if self.ui.line_edit is not None:
             num_sliders = int(self.ui.line_edit.text())
             if len(self.sliders) > num_sliders:
                 for extra_line in self.sliders[num_sliders:]:
                     self.layout.removeWidget(extra_line)
                     extra_line.setParent(None)
 
                 self.sliders = self.sliders[0:num_sliders]
             elif len(self.sliders) < num_sliders:
                 for i in range(num_sliders - len(self.sliders)):
                     widget = SliderLine(self.default_left_color, self.default_right_color, self)
                     self.sliders.append(widget)
                     self.layout.addWidget(widget)
         self.write_settings()
 
     def get_color_space(self):
         if self.canvas() is not None:
             if self.canvas().view() is not None:
                 canvas_color = self.canvas().view().foregroundColor()
                 return ManagedColor(canvas_color.colorModel(), canvas_color.colorDepth(), canvas_color.colorProfile())
         return ManagedColor('RGBA', 'U8', 'sRGB-elle-V2-srgbtrc.icc')
 
     def init_ui(self):
         self.ui = UIMixerSliderDocker()
         self.ui.initialize(self)
 
     def write_settings(self):
         main_program = Krita.instance()
         setting = ';'.join(
             [self.color_to_settings(line.left) + '|' + self.color_to_settings(line.right)
              for line in self.sliders])
 
         main_program.writeSetting("", "MixerSliderColors", setting)
 
     def color_to_settings(self, managedcolor):
         return ','.join([managedcolor.colorModel(),
                          managedcolor.colorDepth(),
                          managedcolor.colorProfile()] +
                         [str(c) for c in managedcolor.components()])
 
     def parse_color(self, array):
         color = ManagedColor(array[0], array[1], array[2])
         color.setComponents([float(x) for x in array[3:]])
         return color
 
     def canvasChanged(self, canvas):
         pass
 
     def qcolor_to_managedcolor(self, qcolor):
         mc = ManagedColor.fromQColor(qcolor, self.canvas())
         return mc
 
     def managedcolor_to_qcolor(self, managedcolor):
         return managedcolor.colorForCanvas(self.canvas())
 
 Application.addDockWidgetFactory(DockWidgetFactory("mixer_slider_docker", DockWidgetFactoryBase.DockRight, MixerSliderDocker))