diff --git a/src/components/main/layout/box_builder.rs b/src/components/main/layout/box_builder.rs
index 3e3f5a6c25b..77366fc5e01 100644
--- a/src/components/main/layout/box_builder.rs
+++ b/src/components/main/layout/box_builder.rs
@@ -291,34 +291,47 @@ impl LayoutTreeBuilder {
     /// Creates necessary box(es) and flow context(s) for the current DOM node,
     /// and recurses on its children.
     pub fn construct_recursively<'a>(&mut self,
-                             layout_ctx: &LayoutContext,
-                             cur_node: AbstractNode<LayoutView>,
-                             mut parent_generator: BoxGenerator<'a>,
-                             mut prev_sibling_generator: Option<BoxGenerator<'a>>)
-                             -> Option<BoxGenerator<'a>> {
+                                     layout_ctx: &LayoutContext,
+                                     cur_node: AbstractNode<LayoutView>,
+                                     mut grandparent_generator: Option<BoxGenerator<'a>>,
+                                     mut parent_generator: BoxGenerator<'a>,
+                                     mut prev_sibling_generator: Option<BoxGenerator<'a>>)
+                                     -> Option<BoxGenerator<'a>> {
         debug!("Considering node: %s", cur_node.debug_str());
         let box_gen_result = {
+            let grandparent_gen_ref = match grandparent_generator {
+                Some(ref mut generator) => Some(generator),
+                None => None,
+            };
             let sibling_gen_ref = match prev_sibling_generator {
                 Some(ref mut generator) => Some(generator),
                 None => None,
             };
-            self.box_generator_for_node(cur_node, &mut parent_generator, sibling_gen_ref)
+            self.box_generator_for_node(cur_node, grandparent_gen_ref, &mut parent_generator, sibling_gen_ref)
         };
 
         debug!("result from generator_for_node: %?", &box_gen_result);
         // Skip over nodes that don't belong in the flow tree
         let (this_generator, next_generator) = 
-            match  box_gen_result {
+            match box_gen_result {
                 NoGenerator => return prev_sibling_generator,
-                ParentGenerator => (parent_generator, None),
+                ParentGenerator => {
+                    do parent_generator.with_clone |clone| {
+                        (clone, None)
+                    }
+                }
                 SiblingGenerator => (prev_sibling_generator.take_unwrap(), None),
                 NewGenerator(gen) => (gen, None),
                 Mixed(gen, next_gen) => (gen, Some(match *next_gen {
-                    ParentGenerator => parent_generator,
+                    ParentGenerator => {
+                        do parent_generator.with_clone |clone| {
+                            clone
+                        }
+                    }
                     SiblingGenerator => prev_sibling_generator.take_unwrap(),
                     _ => fail!("Unexpect BoxGenResult")
                 }))
-        };
+            };
 
 
 
@@ -331,10 +344,17 @@ impl LayoutTreeBuilder {
         // recurse on child nodes.
         let prev_gen_cell = Cell::new(None);
         for child_node in cur_node.children() {
-            do this_generator.with_clone |clone| {
-                let mut prev_generator = prev_gen_cell.take();
-                prev_generator = self.construct_recursively(layout_ctx, child_node, clone, prev_generator);
-                prev_gen_cell.put_back(prev_generator);
+            do parent_generator.with_clone |grandparent_clone| {
+                let grandparent_clone_cell = Cell::new(Some(grandparent_clone));
+                do this_generator.with_clone |parent_clone| {
+                    let mut prev_generator = prev_gen_cell.take();
+                    prev_generator = self.construct_recursively(layout_ctx,
+                                                                child_node,
+                                                                grandparent_clone_cell.take(),
+                                                                parent_clone,
+                                                                prev_generator);
+                    prev_gen_cell.put_back(prev_generator);
+                }
             }
         }
 
@@ -349,11 +369,12 @@ impl LayoutTreeBuilder {
 
     
 
-    pub fn box_generator_for_node<'a>(&mut self, 
-                              node: AbstractNode<LayoutView>, 
-                              parent_generator: &mut BoxGenerator<'a>,
-                              mut sibling_generator: Option<&mut BoxGenerator<'a>>)
-                              -> BoxGenResult<'a> {
+    pub fn box_generator_for_node<'a>(&mut self,
+                                      node: AbstractNode<LayoutView>,
+                                      grandparent_generator: Option<&mut BoxGenerator<'a>>,
+                                      parent_generator: &mut BoxGenerator<'a>,
+                                      mut sibling_generator: Option<&mut BoxGenerator<'a>>)
+                                      -> BoxGenResult<'a> {
 
         let display = if node.is_element() {
             match node.style().display(node.is_root()) {
@@ -468,6 +489,17 @@ impl LayoutTreeBuilder {
 
             // TODO(eatkinson): blocks that are children of inlines need
             // to split their parent flows.
+            (CSSDisplayBlock, & &InlineFlow(*), _) => {
+                match grandparent_generator {
+                    None => fail!("expected to have a grandparent block flow"),
+                    Some(grandparent_gen) => {
+                        assert!(grandparent_gen.flow.is_block_like());
+
+                        self.create_child_generator(node, grandparent_gen, Flow_Block)
+                    }
+                }
+            }
+
             _ => return ParentGenerator
         };
 
@@ -590,7 +622,7 @@ impl LayoutTreeBuilder {
         let mut new_flow = self.make_flow(Flow_Root, root);
         {
             let new_generator = BoxGenerator::new(&mut new_flow);
-            self.construct_recursively(layout_ctx, root, new_generator, None);
+            self.construct_recursively(layout_ctx, root, None, new_generator, None);
         }
         return Ok(new_flow)
     }
diff --git a/src/components/main/layout/flow.rs b/src/components/main/layout/flow.rs
index 9228a6a9911..f5aec1d6fb6 100644
--- a/src/components/main/layout/flow.rs
+++ b/src/components/main/layout/flow.rs
@@ -130,7 +130,14 @@ impl FlowContext {
 }
 
 impl<'self> FlowContext {
-    pub fn leaf(&self) -> bool {
+    pub fn is_block_like(&self) -> bool {
+        match *self {
+            BlockFlow(*) | FloatFlow(*) => true,
+            _ => false,
+        }
+    }
+
+    pub fn is_leaf(&self) -> bool {
         do self.with_base |base| {
             base.children.len() == 0
         }