diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index dc22743..5d7f46f 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -3168,4 +3168,21 @@
   call delete('XtestPopupSign')
 endfunc
 
+func Test_popupwin_bufnr()
+  let popwin = popup_create(['blah'], #{})
+  let popbuf = winbufnr(popwin)
+  split asdfasdf
+  let newbuf = bufnr()
+  call assert_true(newbuf > popbuf, 'New buffer number is higher')
+  call assert_equal(newbuf, bufnr('$'))
+  call popup_clear()
+  let popwin = popup_create(['blah'], #{})
+  " reuses previous buffer number
+  call assert_equal(popbuf, winbufnr(popwin))
+  call assert_equal(newbuf, bufnr('$'))
+
+  call popup_clear()
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2