diff --git a/packages/react-server/src/ReactFlightServer.js b/packages/react-server/src/ReactFlightServer.js
index aefcf5f6ee8..0fcd8af7cbc 100644
--- a/packages/react-server/src/ReactFlightServer.js
+++ b/packages/react-server/src/ReactFlightServer.js
@@ -2302,6 +2302,9 @@ function renderModel(
   key: string,
   value: ReactClientValue,
 ): ReactJSONValue {
+  // First time we're serializing the key, we should add it to the size.
+  serializedSize += key.length;
+
   const prevKeyPath = task.keyPath;
   const prevImplicitSlot = task.implicitSlot;
   try {
@@ -2416,8 +2419,6 @@ function renderModelDestructive(
   // Set the currently rendering model
   task.model = value;
 
-  serializedSize += parentPropertyName.length;
-
   // Special Symbol, that's very common.
   if (value === REACT_ELEMENT_TYPE) {
     return '$';