diff --git a/glib/gmain.c b/glib/gmain.c
index 94aa1152a..f33f55fd1 100644
--- a/glib/gmain.c
+++ b/glib/gmain.c
@@ -342,6 +342,8 @@ struct _GChildWatchSource
 {
   GSource     source;
   GPid        pid;
+  /* On Unix this is a wait status, which is the thing you pass to WEXITSTATUS()
+   * to get the status returned from the process’ main() or passed to exit(): */
   gint        child_status;
 #ifdef G_OS_WIN32
   GPollFD     poll;