diff --git a/src/testdir/test_gui.vim b/src/testdir/test_gui.vim
index 427bab7..50a629b 100644
--- a/src/testdir/test_gui.vim
+++ b/src/testdir/test_gui.vim
@@ -16,7 +16,7 @@
 endfunc
 
 " Test for resetting "secure" flag after GUI has started.
-" Must be run first.
+" Must be run first, since it starts the GUI on Unix.
 func Test_1_set_secure()
   set exrc secure
   gui -f