diff --git a/.babelrc b/.babelrc
index f9a07bc9ff..e7a4ea8497 100644
--- a/.babelrc
+++ b/.babelrc
@@ -1,5 +1,6 @@
 {
   "stage": 0,
   "loose": ["all"],
-  "blacklist": ["es6.tailCall"]
+  "blacklist": ["es6.tailCall"],
+  "optional": ["optimisation.flow.forOf"]
 }
diff --git a/src/babel/generation/index.js b/src/babel/generation/index.js
index 26b7f749f7..bcd9146b0d 100644
--- a/src/babel/generation/index.js
+++ b/src/babel/generation/index.js
@@ -151,7 +151,7 @@ class CodeGenerator {
     // catch up to this nodes newline if we're behind
     if (node.loc && this.format.retainLines && this.buffer.buf) {
       var needsParens = false;
-      if (parent && (this.position.line < node.loc.start.line) && t.isTerminatorless(parent)) {
+      if (parent && this.position.line < node.loc.start.line && t.isTerminatorless(parent)) {
         needsParens = true;
         this._push("(");
       }
diff --git a/src/babel/traversal/context.js b/src/babel/traversal/context.js
index 1e9dd23183..21aacf14d7 100644
--- a/src/babel/traversal/context.js
+++ b/src/babel/traversal/context.js
@@ -32,7 +32,6 @@ export default class TraversalContext {
     for (let i = 0; i < queue.length; i++) {
       var path = queue[i];
       if (visited.indexOf(path.node) >= 0) continue;
-
       visited.push(path.node);
 
       if (path.visit()) {
diff --git a/src/babel/types/converters.js b/src/babel/types/converters.js
index a528497088..9a8faec76e 100644
--- a/src/babel/types/converters.js
+++ b/src/babel/types/converters.js
@@ -43,8 +43,7 @@ export function toSequenceExpression(nodes: Array<Object>, scope: Scope): Object
     var ensureLastUndefined = false;
     var exprs   = [];
 
-    for (let i = 0; i < nodes.length; i++) {
-      var node = nodes[i];
+    for (let node of (nodes: Array)) {
       if (t.isExpression(node)) {
         exprs.push(node);
       } else if (t.isExpressionStatement(node)) {
diff --git a/src/babel/types/index.js b/src/babel/types/index.js
index 3b31d88688..afefeac01e 100644
--- a/src/babel/types/index.js
+++ b/src/babel/types/index.js
@@ -79,8 +79,8 @@ export function isType(nodeType, targetType) {
 
   var aliases = t.FLIPPED_ALIAS_KEYS[targetType];
   if (aliases) {
-    for (var i = 0; i < aliases.length; i++) {
-      if (nodeType === aliases[i]) return true;
+    for (var alias of (aliases: Array)) {
+      if (nodeType === alias) return true;
     }
   }
 
@@ -122,9 +122,7 @@ each(t.BUILDER_KEYS, function (keys, type) {
 export function shallowEqual(actual: Object, expected: Object): boolean {
   var keys = Object.keys(expected);
 
-  for (var i = 0; i < keys.length; i++) {
-    var key = keys[i];
-
+  for (var key of (keys: Array)) {
     if (actual[key] !== expected[key]) {
       return false;
     }
diff --git a/src/babel/types/retrievers.js b/src/babel/types/retrievers.js
index b88a82bfe3..d325aded1f 100644
--- a/src/babel/types/retrievers.js
+++ b/src/babel/types/retrievers.js
@@ -23,8 +23,7 @@ export function getBindingIdentifiers(node: Object): Object {
         search.push(node.declaration);
       }
     } else if (keys) {
-      for (var i = 0; i < keys.length; i++) {
-        var key = keys[i];
+      for (var key of (keys: Array)) {
         search = search.concat(id[key] || []);
       }
     }
diff --git a/src/babel/types/validators.js b/src/babel/types/validators.js
index 2c57deac1d..cbf82b33ee 100644
--- a/src/babel/types/validators.js
+++ b/src/babel/types/validators.js
@@ -42,8 +42,7 @@ export function isReferenced(node: Object, parent: Object): boolean {
     case "ArrowFunctionExpression":
     case "FunctionDeclaration":
     case "FunctionExpression":
-      for (var i = 0; i < parent.params.length; i++) {
-        var param = parent.params[i];
+      for (var param of (parent.params: Array)) {
         if (param === node) return false;
       }