diff --git a/src/testdir/view_util.vim b/src/testdir/view_util.vim
index 72786da..1cdce21 100644
--- a/src/testdir/view_util.vim
+++ b/src/testdir/view_util.vim
@@ -54,6 +54,7 @@
 function! NewWindow(height, width) abort
   exe a:height . 'new'
   exe a:width . 'vsp'
+  set winfixwidth winfixheight
   redraw!
 endfunction