diff --git a/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp b/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
index 868d571417..3ce0aee612 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
@@ -961,7 +961,7 @@ Vector<ShadowData> StyleProperties::text_shadow() const
     return shadow(PropertyID::TextShadow);
 }
 
-CSS::BoxSizing StyleProperties::box_sizing() const
+Optional<CSS::BoxSizing> StyleProperties::box_sizing() const
 {
     auto value = property(CSS::PropertyID::BoxSizing);
     if (!value.has_value())
diff --git a/Userland/Libraries/LibWeb/CSS/StyleProperties.h b/Userland/Libraries/LibWeb/CSS/StyleProperties.h
index a2676e142e..1a55552440 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleProperties.h
+++ b/Userland/Libraries/LibWeb/CSS/StyleProperties.h
@@ -74,7 +74,7 @@ public:
     Optional<CSS::Overflow> overflow_x() const;
     Optional<CSS::Overflow> overflow_y() const;
     Vector<CSS::ShadowData> box_shadow() const;
-    CSS::BoxSizing box_sizing() const;
+    Optional<CSS::BoxSizing> box_sizing() const;
     Optional<CSS::PointerEvents> pointer_events() const;
     Variant<CSS::VerticalAlign, CSS::LengthPercentage> vertical_align() const;
     Optional<CSS::FontVariant> font_variant() const;
diff --git a/Userland/Libraries/LibWeb/Layout/Node.cpp b/Userland/Libraries/LibWeb/Layout/Node.cpp
index 81ecad005b..3ce80add85 100644
--- a/Userland/Libraries/LibWeb/Layout/Node.cpp
+++ b/Userland/Libraries/LibWeb/Layout/Node.cpp
@@ -363,7 +363,8 @@ void NodeWithStyle::apply_style(const CSS::StyleProperties& computed_style)
     }
     computed_values.set_background_color(computed_style.color_or_fallback(CSS::PropertyID::BackgroundColor, *this, CSS::InitialValues::background_color()));
 
-    computed_values.set_box_sizing(computed_style.box_sizing());
+    if (auto box_sizing = computed_style.box_sizing(); box_sizing.has_value())
+        computed_values.set_box_sizing(box_sizing.release_value());
 
     if (auto maybe_font_variant = computed_style.font_variant(); maybe_font_variant.has_value())
         computed_values.set_font_variant(maybe_font_variant.release_value());