diff --git a/src/testdir/test_popup.vim b/src/testdir/test_popup.vim
index fdc009f..4ca35b2 100644
--- a/src/testdir/test_popup.vim
+++ b/src/testdir/test_popup.vim
@@ -743,15 +743,19 @@
   let lines =<< trim END
     set previewheight=9
     silent! pedit
-    call setline(1, map(repeat(["ab"], 10), "v:val. v:key"))
+    call setline(1, map(repeat(["ab"], 10), "v:val .. v:key"))
     exec "norm! G\<C-E>\<C-E>"
   END
   call writefile(lines, 'Xscript')
   let buf = RunVimInTerminal('-S Xscript', {})
 
+  " wait for the script to finish
+  call term_wait(buf)
+
   " Test that popup and previewwindow do not overlap.
-  call term_sendkeys(buf, "o\<C-X>\<C-N>")
-  sleep 100m
+  call term_sendkeys(buf, "o")
+  call term_wait(buf, 100)
+  call term_sendkeys(buf, "\<C-X>\<C-N>")
   call VerifyScreenDump(buf, 'Test_popup_and_previewwindow_01', {})
 
   call term_sendkeys(buf, "\<Esc>u")