diff --git a/gnu/packages/mastodon.scm b/gnu/packages/mastodon.scm
index 44f8664997..cbeccdb402 100644
--- a/gnu/packages/mastodon.scm
+++ b/gnu/packages/mastodon.scm
@@ -119,6 +119,7 @@ (define-public tuba
      (list gdk-pixbuf ; so pixbuf loader cache (for webp) is generated
            gettext-minimal
            `(,glib "bin") ; for glib-compile-resources
+           gsettings-desktop-schemas    ; for the org.gnome.system.proxy schema
            pkg-config))
     (inputs
      (list gst-plugins-bad