diff --git a/briar-gtk/briar_gtk/container.py b/briar-gtk/briar_gtk/container.py
index efdb2841849b1a1de22c997385deb6f6a675b8d1..6a16ad87b121959dfb5df8057f5609d31c0704ea 100644
--- a/briar-gtk/briar_gtk/container.py
+++ b/briar-gtk/briar_gtk/container.py
@@ -2,6 +2,8 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 # License-Filename: LICENSE.md
 
+import os
+
 from gi.repository import Gtk
 
 from briar_gtk.define import RESOURCES_DIR
@@ -14,4 +16,4 @@ class Container(Gtk.Overlay):
         self.builder = Gtk.Builder()
 
     def _add_from_resource(self, ui_filename):
-        self.builder.add_from_resource(RESOURCES_DIR + ui_filename)
+        self.builder.add_from_resource(os.path.join(RESOURCES_DIR, ui_filename))
diff --git a/briar-gtk/briar_gtk/define.py b/briar-gtk/briar_gtk/define.py
index c9697246e7104b3ddaf4c967871f9fc4f80fd811..5a9811a40c2da1570218a69a47dc83316e7e53e1 100644
--- a/briar-gtk/briar_gtk/define.py
+++ b/briar-gtk/briar_gtk/define.py
@@ -6,12 +6,14 @@
 # Initial version based on GNOME Lollypop
 # https://gitlab.gnome.org/World/lollypop/blob/1.0.2/lollypop/define.py
 
+import os
+
 from gi.repository import Gio
 
 APPLICATION_ID = "app.briar.gtk"
 APPLICATION_NAME = "Briar"
-RESOURCES_DIR = "/app/briar/gtk/"
-APPLICATION_STYLING_PATH = "resource://" + RESOURCES_DIR + "application.css"
-BRIAR_HEADLESS_JAR = "/app/briar/briar-headless.jar"
+RESOURCES_DIR = os.path.join("/app", "briar", "gtk")
+APPLICATION_STYLING_PATH = "resource:///app/briar/gtk/application.css"
+BRIAR_HEADLESS_JAR = os.path.join("/app", "briar", "briar-headless.jar")
 
 APP = Gio.Application.get_default
diff --git a/briar-gtk/briar_gtk/widgets/about_dialog.py b/briar-gtk/briar_gtk/widgets/about_dialog.py
index e51daacd965013d8c82934e00d218ac1fabc12c8..9b8ea8f8a1ede853203ca8e3e19ee87bf0aad4f3 100644
--- a/briar-gtk/briar_gtk/widgets/about_dialog.py
+++ b/briar-gtk/briar_gtk/widgets/about_dialog.py
@@ -2,6 +2,8 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 # License-Filename: LICENSE.md
 
+import os
+
 from gettext import gettext as _
 
 from gi.repository import Gtk
@@ -23,7 +25,7 @@ class AboutDialogWidget():
 
     def _load_from_builder(self):
         builder = Gtk.Builder()
-        builder.add_from_resource(RESOURCES_DIR + self.ABOUT_UI)
+        builder.add_from_resource(os.path.join(RESOURCES_DIR, self.ABOUT_UI))
         return builder.get_object("about_dialog")
 
     def _extend_about_dialog(self):