diff --git a/src/uproot_browser/tui/browser.py b/src/uproot_browser/tui/browser.py
index 27500d3..bd8bee9 100644
--- a/src/uproot_browser/tui/browser.py
+++ b/src/uproot_browser/tui/browser.py
@@ -139,7 +139,7 @@ def action_toggle_theme(self) -> None:
         theme = "textual-light" if dark else "textual-dark"
 
         if self.plot_widget.item:
-            self.plot_widget.item.theme = "dark" if dark else "default"
+            self.plot_widget.item.theme = "default" if dark else "dark"
         self.theme = theme
 
     def on_uproot_selected(self, message: UprootSelected) -> None:
diff --git a/tests/test_tui.py b/tests/test_tui.py
index d235adb..26ba2bf 100644
--- a/tests/test_tui.py
+++ b/tests/test_tui.py
@@ -18,6 +18,20 @@ async def test_browse_plot() -> None:
         assert pilot.app.query_one("#main-view").current == "plot"
 
 
+async def test_theme_switch() -> None:
+    async with Browser(
+        skhep_testdata.data_path("uproot-Event.root")
+    ).run_test() as pilot:
+        await pilot.press("down", "down", "down", "enter")
+        browser_theme = pilot.app.theme
+        plot_theme = pilot.app.theme
+        await pilot.press("t")
+        new_browser_theme = pilot.app.theme
+        new_plot_theme = pilot.app.theme
+        assert browser_theme != new_browser_theme
+        assert plot_theme != new_plot_theme
+
+
 async def test_browse_empty() -> None:
     async with Browser(
         skhep_testdata.data_path("uproot-empty.root")