diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index a842bb20a9..64bc868cb5 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -3485,7 +3485,8 @@ void scroll_redraw(int up, long count)
   redraw_later(curwin, VALID);
 }
 
-/// Get the count specified after a 'z' command.
+/// Get the count specified after a 'z' command. Only the 'z<CR>', 'zl', 'zh',
+/// 'z<Left>', and 'z<Right>' commands accept a count after 'z'.
 /// @return  true to process the 'z' command and false to skip it.
 static bool nv_z_get_count(cmdarg_T *cap, int *nchar_arg)
 {
diff --git a/src/nvim/testdir/test_diffmode.vim b/src/nvim/testdir/test_diffmode.vim
index 8c20c647f1..007b7e0f14 100644
--- a/src/nvim/testdir/test_diffmode.vim
+++ b/src/nvim/testdir/test_diffmode.vim
@@ -1332,4 +1332,50 @@ func Test_diff_binary()
   set diffopt&vim
 endfunc
 
+" Test for using the 'zi' command to invert 'foldenable' in diff windows (test
+" for the issue fixed by patch 6.2.317)
+func Test_diff_foldinvert()
+  %bw!
+  edit Xfile1
+  new Xfile2
+  new Xfile3
+  windo diffthis
+  " open a non-diff window
+  botright new
+  1wincmd w
+  call assert_true(getwinvar(1, '&foldenable'))
+  call assert_true(getwinvar(2, '&foldenable'))
+  call assert_true(getwinvar(3, '&foldenable'))
+  normal zi
+  call assert_false(getwinvar(1, '&foldenable'))
+  call assert_false(getwinvar(2, '&foldenable'))
+  call assert_false(getwinvar(3, '&foldenable'))
+  normal zi
+  call assert_true(getwinvar(1, '&foldenable'))
+  call assert_true(getwinvar(2, '&foldenable'))
+  call assert_true(getwinvar(3, '&foldenable'))
+
+  " If the current window has 'noscrollbind', then 'zi' should not change
+  " 'foldenable' in other windows.
+  1wincmd w
+  set noscrollbind
+  normal zi
+  call assert_false(getwinvar(1, '&foldenable'))
+  call assert_true(getwinvar(2, '&foldenable'))
+  call assert_true(getwinvar(3, '&foldenable'))
+
+  " 'zi' should not change the 'foldenable' for windows with 'noscrollbind'
+  1wincmd w
+  set scrollbind
+  normal zi
+  call setwinvar(2, '&scrollbind', v:false)
+  normal zi
+  call assert_false(getwinvar(1, '&foldenable'))
+  call assert_true(getwinvar(2, '&foldenable'))
+  call assert_false(getwinvar(3, '&foldenable'))
+
+  %bw!
+  set scrollbind&
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/nvim/testdir/test_normal.vim b/src/nvim/testdir/test_normal.vim
index ffa0cd1807..f18ddb274c 100644
--- a/src/nvim/testdir/test_normal.vim
+++ b/src/nvim/testdir/test_normal.vim
@@ -580,6 +580,7 @@ endfunc
 func Test_normal_z_error()
   call assert_beeps('normal! z2p')
   call assert_beeps('normal! zq')
+  call assert_beeps('normal! cz1')
 endfunc
 
 func Test_normal15_z_scroll_vert()
@@ -619,7 +620,7 @@ func Test_normal15_z_scroll_vert()
   call assert_equal(10, winheight(0))
   exe "norm! z12\<cr>"
   call assert_equal(12, winheight(0))
-  exe "norm! z10\<cr>"
+  exe "norm! z15\<Del>0\<cr>"
   call assert_equal(10, winheight(0))
 
   " Test for z.