diff --git a/Userland/Libraries/LibWeb/Layout/FormattingContext.cpp b/Userland/Libraries/LibWeb/Layout/FormattingContext.cpp
index 82e2aa12fe..2d5c1b7473 100644
--- a/Userland/Libraries/LibWeb/Layout/FormattingContext.cpp
+++ b/Userland/Libraries/LibWeb/Layout/FormattingContext.cpp
@@ -811,36 +811,40 @@ void FormattingContext::compute_position(Box const& box)
 
 FormattingState::IntrinsicSizes FormattingContext::calculate_intrinsic_sizes(Layout::Box const& box) const
 {
+    auto& root_state = m_state.m_root;
+
     // If we have cached intrinsic sizes for this box, use them.
-    auto it = m_state.intrinsic_sizes.find(&box);
-    if (it != m_state.intrinsic_sizes.end())
+    auto it = root_state.intrinsic_sizes.find(&box);
+    if (it != root_state.intrinsic_sizes.end())
         return it->value;
 
     // Nothing cached, perform two throwaway layouts to determine the intrinsic sizes.
     // FIXME: This should handle replaced elements with "native" intrinsic size properly!
 
-    auto& cached_box_sizes = m_state.intrinsic_sizes.ensure(&box);
+    FormattingState::IntrinsicSizes cached_box_sizes;
     auto const& containing_block = *box.containing_block();
     {
         FormattingState throwaway_state(&m_state);
-        throwaway_state.get_mutable(containing_block).content_width = INFINITY;
-        throwaway_state.get_mutable(containing_block).content_height = INFINITY;
+        auto& containing_block_state = throwaway_state.get_mutable(containing_block);
+        containing_block_state.content_width = INFINITY;
+        containing_block_state.content_height = INFINITY;
         auto independent_formatting_context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
         VERIFY(independent_formatting_context);
 
         independent_formatting_context->run(box, LayoutMode::OnlyRequiredLineBreaks);
-        cached_box_sizes.max_content_size.set_width(greatest_child_width(throwaway_state, box));
+        cached_box_sizes.max_content_size.set_width(independent_formatting_context->greatest_child_width(box));
         cached_box_sizes.max_content_size.set_height(BlockFormattingContext::compute_theoretical_height(throwaway_state, box));
     }
 
     {
         FormattingState throwaway_state(&m_state);
-        throwaway_state.get_mutable(containing_block).content_width = 0;
-        throwaway_state.get_mutable(containing_block).content_height = 0;
+        auto& containing_block_state = throwaway_state.get_mutable(containing_block);
+        containing_block_state.content_width = 0;
+        containing_block_state.content_height = 0;
         auto independent_formatting_context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
         VERIFY(independent_formatting_context);
         independent_formatting_context->run(box, LayoutMode::AllPossibleLineBreaks);
-        cached_box_sizes.min_content_size.set_width(greatest_child_width(throwaway_state, box));
+        cached_box_sizes.min_content_size.set_width(independent_formatting_context->greatest_child_width(box));
         cached_box_sizes.min_content_size.set_height(BlockFormattingContext::compute_theoretical_height(throwaway_state, box));
     }
 
@@ -856,6 +860,7 @@ FormattingState::IntrinsicSizes FormattingContext::calculate_intrinsic_sizes(Lay
         cached_box_sizes.max_content_size.set_height(tmp);
     }
 
+    root_state.intrinsic_sizes.set(&box, cached_box_sizes);
     return cached_box_sizes;
 }