diff --git a/gobject/gobject.h b/gobject/gobject.h
index f62f9c902..d74bebc7c 100644
--- a/gobject/gobject.h
+++ b/gobject/gobject.h
@@ -238,6 +238,11 @@ typedef void (*GObjectFinalizeFunc)     (GObject      *object);
  * Since the object is already being disposed when the #GWeakNotify is called,
  * there's not much you could do with the object, apart from e.g. using its
  * address as hash-index or the like.
+ *
+ * In particular, this means it’s invalid to call g_object_ref(),
+ * g_weak_ref_init(), g_weak_ref_set(), g_object_add_toggle_ref(),
+ * g_object_weak_ref(), g_object_add_weak_pointer() or any function which calls
+ * them on the object from this callback.
  */
 typedef void (*GWeakNotify)		(gpointer      data,
 					 GObject      *where_the_object_was);