diff --git a/src/testdir/test_preview.vim b/src/testdir/test_preview.vim
index 628ad2b..1bf1d3f 100644
--- a/src/testdir/test_preview.vim
+++ b/src/testdir/test_preview.vim
@@ -25,6 +25,7 @@
   " Go to the preview window
   wincmd P
   call assert_equal(1, &previewwindow)
+  call assert_equal('preview', win_gettype())
 
   " Close preview window
   wincmd z