diff --git a/src/nvim/api/window.c b/src/nvim/api/window.c
index 5a4972ef23..ee7729ce81 100644
--- a/src/nvim/api/window.c
+++ b/src/nvim/api/window.c
@@ -476,6 +476,7 @@ void nvim_win_set_hl_ns(Window window, Integer ns_id, Error *err)
   }
 
   win->w_ns_hl = (NS)ns_id;
+  win->w_ns_hl_winhl = -1;
   win->w_hl_needs_update = true;
   redraw_later(win, UPD_NOT_VALID);
 }
diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index d33734ccfe..a8f3fc45b9 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -1035,7 +1035,7 @@ struct window_S {
   synblock_T *w_s;                 ///< for :ownsyntax
 
   int w_ns_hl;
-  int w_ns_hl_winhl;
+  int w_ns_hl_winhl;  ///< when set to -1, 'winhighlight' shouldn't be used
   int w_ns_hl_active;
   int *w_ns_hl_attr;
 
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 1cfe4cd08b..d3cbe9f056 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -1736,8 +1736,14 @@ bool parse_winhl_opt(const char *winhl, win_T *wp)
     p = wp->w_p_winhl;
   }
 
+  if (wp != NULL && wp->w_ns_hl_winhl < 0) {
+    // 'winhighlight' shouldn't be used for this window.
+    // Only check that the value is valid.
+    wp = NULL;
+  }
+
   if (!*p) {
-    if (wp != NULL && wp->w_ns_hl_winhl && wp->w_ns_hl == wp->w_ns_hl_winhl) {
+    if (wp != NULL && wp->w_ns_hl_winhl > 0 && wp->w_ns_hl == wp->w_ns_hl_winhl) {
       wp->w_ns_hl = 0;
       wp->w_hl_needs_update = true;
     }
diff --git a/test/functional/api/highlight_spec.lua b/test/functional/api/highlight_spec.lua
index dd0611f184..1bbfe203b6 100644
--- a/test/functional/api/highlight_spec.lua
+++ b/test/functional/api/highlight_spec.lua
@@ -710,4 +710,18 @@ describe('API: set/get highlight namespace', function()
     api.nvim_win_set_hl_ns(0, ns)
     eq(ns, api.nvim_get_hl_ns({ winid = 0 }))
   end)
+
+  it('setting namespace takes priority over &winhighlight', function()
+    command('set winhighlight=Visual:Search')
+    n.insert('foobar')
+    local ns = api.nvim_create_namespace('')
+    api.nvim_win_set_hl_ns(0, ns)
+    eq(ns, api.nvim_get_hl_ns({ winid = 0 }))
+    command('enew') -- switching buffer keeps namespace #30904
+    eq(ns, api.nvim_get_hl_ns({ winid = 0 }))
+    command('set winhighlight=')
+    eq(ns, api.nvim_get_hl_ns({ winid = 0 }))
+    command('set winhighlight=Visual:Search')
+    eq(ns, api.nvim_get_hl_ns({ winid = 0 }))
+  end)
 end)