diff --git a/packages/babel-plugin-transform-block-scoping/src/index.js b/packages/babel-plugin-transform-block-scoping/src/index.js
index 184ac5a3f271..f9fd167af832 100644
--- a/packages/babel-plugin-transform-block-scoping/src/index.js
+++ b/packages/babel-plugin-transform-block-scoping/src/index.js
@@ -340,7 +340,9 @@ const loopVisitor = {
 
 function extendMap(map, obj) {
   for (const key of Object.keys(obj)) {
-    map.set(key, obj[key]);
+    if (Object.prototype.hasOwnProperty.call(obj, key)) {
+      map.set(key, obj[key]);
+    }
   }
 }