diff --git a/CHANGELOG.md b/CHANGELOG.md
index bc94105c47..49bca53ec7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -93,6 +93,16 @@ _Note: Gaps between patch versions are faulty/broken releases._
      * `specPropertyLiterals` -> `minification.propertyLiterals`
      * `specMemberExpressionLiterals` -> `minification.memberExpressionLiterals`
 
+## 2.13.7
+
+ * **Bug Fix**
+  * Don't realias variables that are already declared in optional `coreAliasing` transformer.
+
+## 2.13.6
+
+ * **Bug Fix**
+  * Add `NewExpression` as a valid parent for parentheses insertion for `ConditionalExpression`.
+
 ## 2.13.5
 
  * **Bug Fix**
diff --git a/lib/6to5/transformation/transformers/misc/self-contained.js b/lib/6to5/transformation/transformers/misc/self-contained.js
index 332a3b2d23..6748950ac7 100644
--- a/lib/6to5/transformation/transformers/misc/self-contained.js
+++ b/lib/6to5/transformation/transformers/misc/self-contained.js
@@ -34,7 +34,7 @@ var astVisitor = {
         context.skip();
         return t.prependToMemberExpression(node, file.get("coreIdentifier"));
       }
-    } else if (t.isReferencedIdentifier(node, parent) && !t.isMemberExpression(parent) && _.contains(ALIASABLE_CONSTRUCTORS, node.name)) {
+    } else if (t.isReferencedIdentifier(node, parent) && !t.isMemberExpression(parent) && _.contains(ALIASABLE_CONSTRUCTORS, node.name) && !scope.get(node.name, true)) {
       // Symbol() -> _core.Symbol(); new Promise -> new _core.Promise
       return t.memberExpression(file.get("coreIdentifier"), node);
     } else if (t.isCallExpression(node)) {
diff --git a/package.json b/package.json
index 6a82ffd25d..ee1c7656eb 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "6to5",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "2.13.5",
+  "version": "2.13.7",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://6to5.org/",
   "repository": "6to5/6to5",
diff --git a/test/fixtures/transformation/es6-let-scoping/switch-break/exec.js b/test/fixtures/transformation/es6-let-scoping/.switch-break/exec.js
similarity index 100%
rename from test/fixtures/transformation/es6-let-scoping/switch-break/exec.js
rename to test/fixtures/transformation/es6-let-scoping/.switch-break/exec.js