diff --git a/packages/babel-plugin-transform-es2015-block-scoping/src/index.js b/packages/babel-plugin-transform-es2015-block-scoping/src/index.js
index a5a1d45cd4..40275602dd 100644
--- a/packages/babel-plugin-transform-es2015-block-scoping/src/index.js
+++ b/packages/babel-plugin-transform-es2015-block-scoping/src/index.js
@@ -459,8 +459,8 @@ class BlockScoping {
     this.hoistVarDeclarations();
 
     // turn outsideLetReferences into an array
-    const params = values(outsideRefs);
     const args = values(outsideRefs);
+    const params = args.map(id => t.clone(id));
 
     const isSwitch = this.blockPath.isSwitchStatement();
 
diff --git a/packages/babel-preset-es2015/test/fixtures/preset-options/6025/expected.js b/packages/babel-preset-es2015/test/fixtures/preset-options/6025/expected.js
index e0a1c0a0b9..798a5ae27b 100644
--- a/packages/babel-preset-es2015/test/fixtures/preset-options/6025/expected.js
+++ b/packages/babel-preset-es2015/test/fixtures/preset-options/6025/expected.js
@@ -12,9 +12,9 @@ var _iteratorError = undefined;
 
 try {
   for (var _iterator = c[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
-    var path = _step.value;
+    var _path = _step.value;
 
-    _loop(path);
+    _loop(_path);
   }
 } catch (err) {
   _didIteratorError = true;