diff --git a/data/gui/advanced_configuration_window.ui b/data/gui/advanced_configuration_window.ui
index 52df66599d40ac2a0eaa0b25b1cfa313c001391b..72c058b157fa69ae1cba45c71a831bd677663a4c 100644
--- a/data/gui/advanced_configuration_window.ui
+++ b/data/gui/advanced_configuration_window.ui
@@ -5,6 +5,7 @@
     <property name="can_focus">False</property>
     <property name="border_width">6</property>
     <property name="title" translatable="yes">Advanced Configuration Editor</property>
+    <property name="window_position">center-on-parent</property>
     <property name="role">ace</property>
     <property name="default_width">650</property>
     <property name="default_height">540</property>
diff --git a/data/gui/gajim_themes_window.ui b/data/gui/gajim_themes_window.ui
index 9b45b421ed689a0bbe8db389ab4dcdcb3ee67d3e..fbc921f39c3685881caf638d6992f334c8ce4ecf 100644
--- a/data/gui/gajim_themes_window.ui
+++ b/data/gui/gajim_themes_window.ui
@@ -25,6 +25,7 @@
   <object class="GtkWindow" id="gajim_themes_window">
     <property name="border_width">12</property>
     <property name="title" translatable="yes">Gajim Themes Customization</property>
+    <property name="window_position">center-on-parent</property>
     <property name="type_hint">dialog</property>
     <child>
       <object class="GtkVBox" id="vbox97">
diff --git a/data/gui/manage_sounds_window.ui b/data/gui/manage_sounds_window.ui
index b1243a1eb4f26606383a0a76e5506b5736b689e9..798413880ca18ebae7ab9972ba125e1c2d0cd494 100644
--- a/data/gui/manage_sounds_window.ui
+++ b/data/gui/manage_sounds_window.ui
@@ -7,6 +7,7 @@
     <property name="height_request">350</property>
     <property name="border_width">6</property>
     <property name="title" translatable="yes">Manage sounds</property>
+    <property name="window_position">center-on-parent</property>
     <property name="type_hint">dialog</property>
     <signal name="delete_event" handler="on_manage_sounds_window_delete_event"/>
     <child>