diff --git a/src/nvim/api/win_config.c b/src/nvim/api/win_config.c
index f92502e6c9..65e25a20b4 100644
--- a/src/nvim/api/win_config.c
+++ b/src/nvim/api/win_config.c
@@ -211,12 +211,12 @@ Window nvim_open_win(Buffer buf, Boolean enter, Dict(win_config) *config, Error
     return 0;
   }
 
+  bool is_split = HAS_KEY_X(config, split) || HAS_KEY_X(config, vertical);
   WinConfig fconfig = WIN_CONFIG_INIT;
-  if (!parse_win_config(NULL, config, &fconfig, false, err)) {
+  if (!parse_win_config(NULL, config, &fconfig, false, !is_split, err)) {
     return 0;
   }
 
-  bool is_split = HAS_KEY_X(config, split) || HAS_KEY_X(config, vertical);
   Window rv = 0;
   if (fconfig.noautocmd) {
     block_autocmds();
@@ -771,8 +771,9 @@ void nvim_win_set_config(Window win, Dict(win_config) *config, Error *err)
   bool to_split = config->relative.size == 0
                   && !(HAS_KEY_X(config, external) && config->external)
                   && (has_split || has_vertical || was_split);
+  bool will_float = (!was_split && !to_split) || config->relative.size > 0 || config->external;
 
-  if (!parse_win_config(w, config, &fconfig, !was_split || to_split, err)) {
+  if (!parse_win_config(w, config, &fconfig, !was_split || to_split, will_float, err)) {
     return;
   }
 
@@ -1258,7 +1259,7 @@ bool parse_winborder(WinConfig *fconfig, char *border_opt, Error *err)
 }
 
 static bool parse_win_config(win_T *wp, Dict(win_config) *config, WinConfig *fconfig, bool reconf,
-                             Error *err)
+                             bool will_float, Error *err)
 {
   bool has_relative = false, relative_is_win = false, is_split = false;
   if (config->relative.size > 0) {
@@ -1423,7 +1424,7 @@ static bool parse_win_config(win_T *wp, Dict(win_config) *config, WinConfig *fco
   }
 
   if (HAS_KEY_X(config, zindex)) {
-    VALIDATE_CON(!is_split, "zindex", "non-float window", {
+    VALIDATE_CON(will_float, "zindex", "non-float window", {
       goto fail;
     });
     VALIDATE_EXP((config->zindex > 0), "zindex", "positive Integer", NULL, {
@@ -1433,7 +1434,7 @@ static bool parse_win_config(win_T *wp, Dict(win_config) *config, WinConfig *fco
   }
 
   if (HAS_KEY_X(config, title)) {
-    VALIDATE_CON(!is_split, "title", "non-float window", {
+    VALIDATE_CON(will_float, "title", "non-float window", {
       goto fail;
     });
 
@@ -1453,7 +1454,7 @@ static bool parse_win_config(win_T *wp, Dict(win_config) *config, WinConfig *fco
   }
 
   if (HAS_KEY_X(config, footer)) {
-    VALIDATE_CON(!is_split, "footer", "non-float window", {
+    VALIDATE_CON(will_float, "footer", "non-float window", {
       goto fail;
     });
 
@@ -1474,7 +1475,7 @@ static bool parse_win_config(win_T *wp, Dict(win_config) *config, WinConfig *fco
 
   Object border_style = OBJECT_INIT;
   if (HAS_KEY_X(config, border)) {
-    VALIDATE_CON(!is_split, "border", "non-float window", {
+    VALIDATE_CON(will_float, "border", "non-float window", {
       goto fail;
     });
     border_style = config->border;
@@ -1514,6 +1515,9 @@ static bool parse_win_config(win_T *wp, Dict(win_config) *config, WinConfig *fco
   }
 
   if (HAS_KEY_X(config, hide)) {
+    VALIDATE_CON(will_float || !config->hide, "hide", "non-float window", {
+      goto fail;
+    });
     if (fconfig->hide && !config->hide) {
       redraw_later(wp, UPD_NOT_VALID);
     }
diff --git a/test/functional/ui/float_spec.lua b/test/functional/ui/float_spec.lua
index 8978ccd783..59ee0eb0e5 100644
--- a/test/functional/ui/float_spec.lua
+++ b/test/functional/ui/float_spec.lua
@@ -205,6 +205,13 @@ describe('float window', function()
       "Conflict: 'bufpos' not allowed with non-float window",
       pcall_err(api.nvim_win_set_config, winid, { split = 'right', bufpos = { 0, 0 } })
     )
+
+    -- Reconfiguring split
+    local not_allowed = { hide = true, zindex = 1, title = '', footer = '', border = 'single' }
+    for k, v in pairs(not_allowed) do
+      local err = ("Conflict: '%s' not allowed with non-float window"):format(k)
+      eq(err, pcall_err(api.nvim_win_set_config, winid, { [k] = v }))
+    end
   end)
 
   it('win_execute() should work', function()