diff --git a/components/layout_2020/flow/mod.rs b/components/layout_2020/flow/mod.rs
index 1813e58daad..8331f54ea09 100644
--- a/components/layout_2020/flow/mod.rs
+++ b/components/layout_2020/flow/mod.rs
@@ -134,20 +134,27 @@ impl BlockContainer {
             ),
         }
     }
-
+    
     pub(super) fn inline_content_sizes(
         &self,
         layout_context: &LayoutContext,
         writing_mode: WritingMode,
     ) -> ContentSizes {
         match &self {
-            Self::BlockLevelBoxes(boxes) => boxes
+            Self::BlockLevelBoxes(boxes) if layout_context.use_rayon => boxes
                 .par_iter()
                 .map(|box_| {
                     box_.borrow_mut()
                         .inline_content_sizes(layout_context, writing_mode)
                 })
                 .reduce(ContentSizes::zero, ContentSizes::max),
+            Self::BlockLevelBoxes(boxes) => boxes
+                .iter()
+                .map(|box_| {
+                    box_.borrow_mut()
+                        .inline_content_sizes(layout_context, writing_mode)                    
+                })
+                .reduce(ContentSizes::max).unwrap_or_else(ContentSizes::zero),
             Self::InlineFormattingContext(context) => {
                 context.inline_content_sizes(layout_context, writing_mode)
             },