diff --git a/src/config.py b/src/config.py
index 002221fe5..a289a7555 100644
--- a/src/config.py
+++ b/src/config.py
@@ -1299,7 +1299,7 @@ class ManageProxiesWindow:
     def __init__(self):
         self.xml = gtkgui_helpers.get_gtk_builder('manage_proxies_window.ui')
         self.window = self.xml.get_object('manage_proxies_window')
-        self.set_transient_for(gajim.interface.roster.window)
+        self.window.set_transient_for(gajim.interface.roster.window)
         self.proxies_treeview = self.xml.get_object('proxies_treeview')
         self.proxyname_entry = self.xml.get_object('proxyname_entry')
         self.proxytype_combobox = self.xml.get_object('proxytype_combobox')
@@ -2749,7 +2749,7 @@ class ServiceRegistrationWindow:
         self.is_form = is_form
         self.xml = gtkgui_helpers.get_gtk_builder('service_registration_window.ui')
         self.window = self.xml.get_object('service_registration_window')
-        self.set_transient_for(gajim.interface.roster.window)
+        self.window.set_transient_for(gajim.interface.roster.window)
         if self.is_form:
             dataform = dataforms.ExtendForm(node = infos)
             self.data_form_widget = dataforms_widget.DataFormWidget(dataform)
@@ -2804,7 +2804,7 @@ class GroupchatConfigWindow:
         self.xml = gtkgui_helpers.get_gtk_builder('data_form_window.ui',
             'data_form_window')
         self.window = self.xml.get_object('data_form_window')
-        self.set_transient_for(gajim.interface.roster.window)
+        self.window.set_transient_for(gajim.interface.roster.window)
 
         if self.form:
             config_vbox = self.xml.get_object('config_vbox')
@@ -3023,7 +3023,7 @@ class RemoveAccountWindow:
         self.account = account
         xml = gtkgui_helpers.get_gtk_builder('remove_account_window.ui')
         self.window = xml.get_object('remove_account_window')
-        self.set_transient_for(gajim.interface.roster.window)
+        self.window.set_transient_for(gajim.interface.roster.window)
         self.remove_and_unregister_radiobutton = xml.get_object(
                 'remove_and_unregister_radiobutton')
         self.window.set_title(_('Removing %s account') % self.account)
@@ -3130,7 +3130,7 @@ class ManageBookmarksWindow:
     def __init__(self):
         self.xml = gtkgui_helpers.get_gtk_builder('manage_bookmarks_window.ui')
         self.window = self.xml.get_object('manage_bookmarks_window')
-        self.set_transient_for(gajim.interface.roster.window)
+        self.window.set_transient_for(gajim.interface.roster.window)
 
         # Account-JID, RoomName, Room-JID, Autojoin, Minimize, Passowrd, Nick,
         # Show_Status
@@ -4025,7 +4025,7 @@ class ManagePEPServicesWindow:
     def __init__(self, account):
         self.xml = gtkgui_helpers.get_gtk_builder('manage_pep_services_window.ui')
         self.window = self.xml.get_object('manage_pep_services_window')
-        self.set_transient_for(gajim.interface.roster.window)
+        self.window.set_transient_for(gajim.interface.roster.window)
         self.xml.get_object('configure_button').set_sensitive(False)
         self.xml.get_object('delete_button').set_sensitive(False)
         self.xml.connect_signals(self)
diff --git a/src/dialogs.py b/src/dialogs.py
index 449a01bdb..7a2977774 100644
--- a/src/dialogs.py
+++ b/src/dialogs.py
@@ -287,7 +287,7 @@ class ChooseGPGKeyDialog:
         xml = gtkgui_helpers.get_gtk_builder('choose_gpg_key_dialog.ui')
         self.window = xml.get_object('choose_gpg_key_dialog')
         self.window.set_title(title_text)
-        self.set_transient_for(transient_for)
+        self.window.set_transient_for(transient_for)
         self.keys_treeview = xml.get_object('keys_treeview')
         prompt_label = xml.get_object('prompt_label')
         prompt_label.set_text(prompt_text)
@@ -353,7 +353,7 @@ class ChangeActivityDialog:
         self.text = text
         self.xml = gtkgui_helpers.get_gtk_builder('change_activity_dialog.ui')
         self.window = self.xml.get_object('change_activity_dialog')
-        self.set_transient_for(gajim.interface.roster.window)
+        self.window.set_transient_for(gajim.interface.roster.window)
 
         self.checkbutton = self.xml.get_object('enable_checkbutton')
         self.notebook = self.xml.get_object('notebook')
@@ -476,7 +476,7 @@ class ChangeMoodDialog:
         self.xml = gtkgui_helpers.get_gtk_builder('change_mood_dialog.ui')
 
         self.window = self.xml.get_object('change_mood_dialog')
-        self.set_transient_for(gajim.interface.roster.window)
+        self.window.set_transient_for(gajim.interface.roster.window)
         self.window.set_title(_('Set Mood'))
 
         table = self.xml.get_object('mood_icons_table')
@@ -2359,7 +2359,7 @@ class JoinGroupchatWindow:
         self._empty_required_widgets = []
 
         self.window = self.xml.get_object('join_groupchat_window')
-        self.set_transient_for(gajim.interface.roster.window)
+        self.window.set_transient_for(gajim.interface.roster.window)
         self._room_jid_entry = self.xml.get_object('room_jid_entry')
         self._nickname_entry = self.xml.get_object('nickname_entry')
         self._password_entry = self.xml.get_object('password_entry')
diff --git a/src/gajim_themes_window.py b/src/gajim_themes_window.py
index 29023acfa..6620018c9 100644
--- a/src/gajim_themes_window.py
+++ b/src/gajim_themes_window.py
@@ -34,7 +34,7 @@ class GajimThemesWindow:
     def __init__(self):
         self.xml = gtkgui_helpers.get_gtk_builder('gajim_themes_window.ui')
         self.window = self.xml.get_object('gajim_themes_window')
-        self.set_transient_for(gajim.interface.roster.window)
+        self.window.set_transient_for(gajim.interface.roster.window)
 
         self.options = ['account', 'group', 'contact', 'banner']
         self.options_combobox = self.xml.get_object('options_combobox')