diff --git a/glib/grefcount.c b/glib/grefcount.c
index 7cb12fc46..9dae60ad8 100644
--- a/glib/grefcount.c
+++ b/glib/grefcount.c
@@ -142,6 +142,10 @@ void
  *
  * Decreases the reference count.
  *
+ * If %TRUE is returned, the reference count reached 0. After this point, @rc
+ * is an undefined state and must be reinitialized with
+ * g_ref_count_init() to be used again.
+ *
  * Returns: %TRUE if the reference count reached 0, and %FALSE otherwise
  *
  * Since: 2.58
@@ -249,6 +253,10 @@ void
  *
  * Atomically decreases the reference count.
  *
+ * If %TRUE is returned, the reference count reached 0. After this point, @arc
+ * is an undefined state and must be reinitialized with
+ * g_atomic_ref_count_init() to be used again.
+ *
  * Returns: %TRUE if the reference count reached 0, and %FALSE otherwise
  *
  * Since: 2.58