diff --git a/guix/build-system/meson.scm b/guix/build-system/meson.scm
index d66ec760a4..d7754e460a 100644
--- a/guix/build-system/meson.scm
+++ b/guix/build-system/meson.scm
@@ -67,7 +67,7 @@ (define* (lower name
                 #:key source inputs native-inputs outputs system target
                 (meson (default-meson))
                 (ninja (default-ninja))
-                (glib-or-gtk #f)
+                (glib-or-gtk? #f)
                 #:allow-other-keys
                 #:rest arguments)
   "Return a bag for NAME."