diff --git a/src/textual/app.py b/src/textual/app.py
index 1462eeb3ef..3578e2d751 100644
--- a/src/textual/app.py
+++ b/src/textual/app.py
@@ -480,7 +480,14 @@ def watch_dark(self, dark: bool) -> None:
         """Watches the dark bool."""
         self.set_class(dark, "-dark-mode")
         self.set_class(not dark, "-light-mode")
-        self.refresh_css()
+        try:
+            self.refresh_css()
+        except ScreenStackError:
+            # It's possible that `dark` can be set before we have a default
+            # screen, in an app's `on_load`, for example. So let's eat the
+            # ScreenStackError -- the above styles will be handled once the
+            # screen is spun up anyway.
+            pass
 
     def get_driver_class(self) -> Type[Driver]:
         """Get a driver class for this platform.