--- a/dom/xul/nsXULElement.cpp
+++ b/dom/xul/nsXULElement.cpp
@@ -376,18 +376,17 @@ nsXULElement::Clone(mozilla::dom::NodeIn
     for (uint32_t i = 0; i < count; ++i) {
         const nsAttrName* originalName = mAttrsAndChildren.AttrNameAt(i);
         const nsAttrValue* originalValue = mAttrsAndChildren.AttrAt(i);
         nsAttrValue attrValue;
 
         // Style rules need to be cloned.
         if (originalValue->Type() == nsAttrValue::eCSSDeclaration) {
             DeclarationBlock* decl = originalValue->GetCSSDeclarationValue();
-            RefPtr<css::Declaration>
-              declClone = new css::Declaration(*decl->AsGecko());
+            RefPtr<DeclarationBlock> declClone = decl->Clone();
 
             nsString stringValue;
             originalValue->ToString(stringValue);
 
             attrValue.SetTo(declClone.forget(), &stringValue);
         } else {
             attrValue.SetTo(*originalValue);
         }
@@ -1913,18 +1912,17 @@ nsXULElement::MakeHeavyweight(nsXULProto
     nsresult rv;
     for (i = 0; i < aPrototype->mNumAttributes; ++i) {
         nsXULPrototypeAttribute* protoattr = &aPrototype->mAttributes[i];
         nsAttrValue attrValue;
 
         // Style rules need to be cloned.
         if (protoattr->mValue.Type() == nsAttrValue::eCSSDeclaration) {
             DeclarationBlock* decl = protoattr->mValue.GetCSSDeclarationValue();
-            RefPtr<css::Declaration>
-              declClone = new css::Declaration(*decl->AsGecko());
+            RefPtr<DeclarationBlock> declClone = decl->Clone();
 
             nsString stringValue;
             protoattr->mValue.ToString(stringValue);
 
             attrValue.SetTo(declClone.forget(), &stringValue);
         } else {
             attrValue.SetTo(protoattr->mValue);
         }

--- a/layout/mathml/crashtests/crashtests.list
+++ b/layout/mathml/crashtests/crashtests.list
@@ -46,17 +46,17 @@ load 412237-1.xml
 load 413063-1.xhtml
 load 416907-1.xhtml
 load 420420-1.xhtml
 load 431072-1.xhtml
 load 443089-1.xhtml
 load 463763-1.xhtml
 load 463763-2.xhtml
 load 476547-1.xhtml
-skip-if(stylo) load 477740-1.xhtml # bug 1323702
+load 477740-1.xhtml
 load 541620-1.xhtml
 load 557474-1.html
 load 654928-1.html
 asserts-if(stylo,12) load 655451-1.xhtml # bug 1324660
 load 713606-1.html
 load 716349-1.html
 load 848725-1.html
 load 848725-2.html