diff --git a/shiny/ui/_page.py b/shiny/ui/_page.py
index fcf34b878..7a56b7daa 100644
--- a/shiny/ui/_page.py
+++ b/shiny/ui/_page.py
@@ -94,7 +94,7 @@ def page_sidebar(
             sidebar,
             *children,
             # Make the main area background white instead of the default gray.
-            {"style": "--bslib-shiny-preset-main-bg: white"},
+            {"style": "--bslib-shiny-preset-main-bg: white;"},
             attrs,
             fillable=fillable,
             border=False,