diff --git a/glib/gthread.c b/glib/gthread.c
index 5debfa6ae..a36b37861 100644
--- a/glib/gthread.c
+++ b/glib/gthread.c
@@ -320,6 +320,10 @@
  * simultaneous read-only access (by holding the 'reader' lock via
  * g_rw_lock_reader_lock()).
  *
+ * It is unspecified whether readers or writers have priority in acquiring the
+ * lock when a reader already holds the lock and a writer is queued to acquire
+ * it.
+ *
  * Here is an example for an array with access functions:
  * |[<!-- language="C" --> 
  *   GRWLock lock;