diff --git a/src/babel/transformation/file.js b/src/babel/transformation/file.js
index b22d7eee4b..c508fe147c 100644
--- a/src/babel/transformation/file.js
+++ b/src/babel/transformation/file.js
@@ -118,7 +118,7 @@ export default class File {
 
     for (var key in opts) {
       if (key[0] !== "_" && File.validOptions.indexOf(key) < 0) {
-        throw new ReferenceError("Unknown option: " + key);
+        throw new ReferenceError(`Unknown option: ${key}`);
       }
     }
 
@@ -248,7 +248,7 @@ export default class File {
 
   debug(msg) {
     var parts = this.opts.filename;
-    if (msg) parts += ": " + msg;
+    if (msg) parts += `: ${msg}`;
     util.debug(parts);
   }
 
@@ -261,7 +261,7 @@ export default class File {
     }
 
     if (!ModuleFormatter) {
-      throw new ReferenceError("Unknown module formatter type " + JSON.stringify(type));
+      throw new ReferenceError(`Unknown module formatter type ${JSON.stringify(type)}`);
     }
 
     return new ModuleFormatter(this);
@@ -338,7 +338,7 @@ export default class File {
 
   addHelper(name) {
     if (!includes(File.helpers, name)) {
-      throw new ReferenceError("Unknown helper " + name);
+      throw new ReferenceError(`Unknown helper ${name}`);
     }
 
     var program = this.ast.program;
@@ -371,7 +371,7 @@ export default class File {
 
   errorWithNode(node, msg, Error = SyntaxError) {
     var loc = node.loc.start;
-    var err = new Error("Line " + loc.line + ": " + msg);
+    var err = new Error(`Line ${loc.line}: ${msg}`);
     err.loc = loc;
     return err;
   }
@@ -430,6 +430,13 @@ export default class File {
   }
 
   checkNode(node, scope) {
+    if (Array.isArray(node)) {
+      for (var i = 0; i < node.length; i++) {
+        this.checkNode(node[i], scope);
+      }
+      return;
+    }
+
     var stack = this.transformerStack;
     scope ||= this.scope;
 
@@ -463,7 +470,7 @@ export default class File {
 
     if (this.shebang) {
       // add back shebang
-      result.code = this.shebang + "\n" + result.code;
+      result.code = `${this.shebang}\n${result.code}`;
     }
 
     if (opts.sourceMap === "inline") {
diff --git a/src/babel/transformation/transformers/es6/destructuring.js b/src/babel/transformation/transformers/es6/destructuring.js
index 284df2b7aa..2648647e98 100644
--- a/src/babel/transformation/transformers/es6/destructuring.js
+++ b/src/babel/transformation/transformers/es6/destructuring.js
@@ -56,12 +56,12 @@ export { ForOfStatement as ForInStatement };
 exports.Function = function (node, parent, scope, file) {
   var nodes = [];
 
-  var hasDestructuringTransformer = false;
+  var hasDestructuring = false;
 
   node.params = node.params.map(function (pattern, i) {
     if (!t.isPattern(pattern)) return pattern;
 
-    hasDestructuringTransformer = true;
+    hasDestructuring = true;
     var ref = scope.generateUidIdentifier("ref");
 
     var destructuring = new DestructuringTransformer({
@@ -69,15 +69,16 @@ exports.Function = function (node, parent, scope, file) {
       nodes:      nodes,
       scope:      scope,
       file:       file,
-      kind:       "var",
+      kind:       "let"
     });
     destructuring.init(pattern, ref);
 
     return ref;
   });
 
-  if (!hasDestructuringTransformer) return;
+  if (!hasDestructuring) return;
 
+  file.checkNode(nodes);
   t.ensureBlock(node);
 
   var block = node.body;
diff --git a/src/babel/transformation/transformers/es6/parameters.default.js b/src/babel/transformation/transformers/es6/parameters.default.js
index 9632e9db72..e0068685ca 100644
--- a/src/babel/transformation/transformers/es6/parameters.default.js
+++ b/src/babel/transformation/transformers/es6/parameters.default.js
@@ -61,7 +61,7 @@ exports.Function = function (node, parent, scope, file) {
         scope.traverse(param, iifeVisitor, state);
       }
 
-      if (file.transformers["es6.blockScopingTDZ"].canRun()) {
+      if (file.transformers["es6.blockScopingTDZ"].canRun() && t.isIdentifier(param)) {
         pushDefNode(param, t.identifier("undefined"), i);
       }
 
diff --git a/src/babel/transformation/transformers/es6/parameters.rest.js b/src/babel/transformation/transformers/es6/parameters.rest.js
index bdf156a107..c3d0f49bf9 100644
--- a/src/babel/transformation/transformers/es6/parameters.rest.js
+++ b/src/babel/transformation/transformers/es6/parameters.rest.js
@@ -55,7 +55,7 @@ var hasRest = function (node) {
   return t.isRestElement(node.params[node.params.length - 1]);
 };
 
-exports.Function = function (node, parent, scope) {
+exports.Function = function (node, parent, scope, file) {
   if (!hasRest(node)) return;
 
   var rest = node.params.pop().argument;
@@ -69,10 +69,12 @@ exports.Function = function (node, parent, scope) {
   if (t.isPattern(rest)) {
     var pattern = rest;
     rest = scope.generateUidIdentifier("ref");
-    var declar = t.variableDeclaration("var", pattern.elements.map(function (elem, index) {
+
+    var declar = t.variableDeclaration("let", pattern.elements.map(function (elem, index) {
       var accessExpr = t.memberExpression(rest, t.literal(index), true);
       return t.variableDeclarator(elem, accessExpr);
     }));
+    file.checkNode(declar);
     node.body.body.unshift(declar);
   }
 
diff --git a/test/fixtures/transformation/es6-block-scoping-tdz-fail/destructuring.js b/test/fixtures/transformation/es6-block-scoping-tdz-fail/destructuring.js
new file mode 100644
index 0000000000..bfc4f6e119
--- /dev/null
+++ b/test/fixtures/transformation/es6-block-scoping-tdz-fail/destructuring.js
@@ -0,0 +1,9 @@
+function foo(
+   { x: { y: { z: a = b } = {}, w: b = 20 }, a: c = 30 }
+) {
+  assert.equal(a, 10);
+  assert.equal(b, 20);
+  assert.equal(c, 30);
+}
+
+foo({ x: {} });
diff --git a/test/fixtures/transformation/es6-block-scoping-tdz-pass/destructuring.js b/test/fixtures/transformation/es6-block-scoping-tdz-pass/destructuring.js
new file mode 100644
index 0000000000..3a9e4b23b2
--- /dev/null
+++ b/test/fixtures/transformation/es6-block-scoping-tdz-pass/destructuring.js
@@ -0,0 +1,9 @@
+function foo(
+   { x: { y: { z: a = 10 } = {}, w: b = 20 }, a: c = 30 }
+) {
+  assert.equal(a, 10);
+  assert.equal(b, 20);
+  assert.equal(c, 30);
+}
+
+foo({ x: {} });