--- a/dom/xbl/nsXBLPrototypeResources.cpp
+++ b/dom/xbl/nsXBLPrototypeResources.cpp
@@ -106,17 +106,23 @@ nsXBLPrototypeResources::FlushSkinSheets
     }
     else {
       newSheet = oldSheet;
     }
 
     mStyleSheetList.AppendElement(newSheet);
   }
 
-  GatherRuleProcessor();
+  if (doc->IsStyledByServo()) {
+    MOZ_ASSERT(doc->GetShell());
+    MOZ_ASSERT(doc->GetShell()->GetPresContext());
+    ComputeServoStyleSet(doc->GetShell()->GetPresContext());
+  } else {
+    GatherRuleProcessor();
+  }
 
   return NS_OK;
 }
 
 nsresult
 nsXBLPrototypeResources::Write(nsIObjectOutputStream* aStream)
 {
   if (mLoader)