diff --git a/Source/WebCore/rendering/RenderBlockFlow.cpp b/Source/WebCore/rendering/RenderBlockFlow.cpp
index 4795db7..ab54ffb 100644
--- a/Source/WebCore/rendering/RenderBlockFlow.cpp
+++ b/Source/WebCore/rendering/RenderBlockFlow.cpp
@@ -739,7 +739,7 @@
     setLogicalTopForChild(child, logicalTopEstimate, ApplyLayoutDelta);
     estimateFragmentRangeForBoxChild(child);
 
-    RenderBlockFlow* childBlockFlow = is<RenderBlockFlow>(child) ? &downcast<RenderBlockFlow>(child) : nullptr;
+    auto* childBlockFlow = dynamicDowncast<RenderBlockFlow>(child);
     bool markDescendantsWithFloats = false;
     if (logicalTopEstimate != oldLogicalTop && !child.avoidsFloats() && childBlockFlow && childBlockFlow->containsFloats())
         markDescendantsWithFloats = true;
@@ -993,7 +993,7 @@
     LayoutUnit beforeMargin;
     LayoutUnit afterMargin;
 
-    RenderBlockFlow* childRenderBlock = is<RenderBlockFlow>(child) ? &downcast<RenderBlockFlow>(child) : nullptr;
+    auto* childRenderBlock = dynamicDowncast<RenderBlockFlow>(child);
     
     // If the child has the same directionality as we do, then we can just return its
     // margins in the same direction.
@@ -1471,7 +1471,7 @@
 
 LayoutUnit RenderBlockFlow::adjustBlockChildForPagination(LayoutUnit logicalTopAfterClear, LayoutUnit estimateWithoutPagination, RenderBox& child, bool atBeforeSideOfBlock)
 {
-    RenderBlock* childRenderBlock = is<RenderBlock>(child) ? &downcast<RenderBlock>(child) : nullptr;
+    auto* childRenderBlock = dynamicDowncast<RenderBlock>(child);
 
     if (estimateWithoutPagination != logicalTopAfterClear) {
         // Our guess prior to pagination movement was wrong. Before we attempt to paginate, let's try again at the new
@@ -2496,7 +2496,7 @@
             // See if we have a pagination strut that is making us move down further.
             // Note that an unsplittable child can't also have a pagination strut, so this
             // is exclusive with the case above.
-            RenderBlock* childBlock = is<RenderBlock>(childBox) ? &downcast<RenderBlock>(childBox) : nullptr;
+            auto* childBlock = dynamicDowncast<RenderBlock>(childBox);
             if (childBlock && childBlock->paginationStrut()) {
                 newLogicalTop += childBlock->paginationStrut();
                 childBlock->setPaginationStrut(0);