diff --git a/src/program/types/ForOfStatement.js b/src/program/types/ForOfStatement.js
index afe479c0..387ba4ee 100644
--- a/src/program/types/ForOfStatement.js
+++ b/src/program/types/ForOfStatement.js
@@ -33,10 +33,11 @@ export default class ForOfStatement extends LoopStatement {
 
 		const key = scope.createIdentifier( 'i' );
 		const list = scope.createIdentifier( 'list' );
+		const useLen = scope.createIdentifier( 'useLen' );
 
 		if ( this.body.synthetic ) {
 			code.insertRight( this.left.start, `{\n${i1}` );
-			code.insertLeft( this.body.body[0].end, `\n${i0}}` );
+			code.insertLeft( this.body.end, `\n${i0}}` );
 		}
 
 		const bodyStart = this.body.body[0].start;
@@ -46,7 +47,9 @@ export default class ForOfStatement extends LoopStatement {
 
 
 		code.insertRight( this.right.start, `var ${key} = 0, ${list} = ` );
-		code.insertLeft( this.right.end, `; ${key} < ${list}.length; ${key} += 1` );
+		code.insertLeft( this.right.end, `, ${useLen} = typeof ${list}.length === 'number' || typeof Symbol !== 'function', ${list} = ${useLen} ? ${list} : ${list}[Symbol.iterator](); ${useLen} ? ${key} < ${list}.length : !(${key} = ${list}.next()).done;` );
+
+		const getVal = `${useLen} ? ${list}[${key}++] : ${key}.value`;
 
 		// destructuring. TODO non declaration destructuring
 		const declarator = this.left.type === 'VariableDeclaration' && this.left.declarations[0];
@@ -65,9 +68,9 @@ export default class ForOfStatement extends LoopStatement {
 			});
 
 			code.insertLeft( this.left.start + this.left.kind.length + 1, ref );
-			code.insertLeft( this.left.end, ` = ${list}[${key}];\n${i1}` );
+			code.insertLeft( this.left.end, ` = ${getVal};\n${i1}` );
 		} else {
-			code.insertLeft( this.left.end, ` = ${list}[${key}];\n\n${i1}` );
+			code.insertLeft( this.left.end, ` = ${getVal};\n\n${i1}` );
 		}
 
 		super.transpile( code, transforms );
diff --git a/test/samples/for-of.js b/test/samples/for-of.js
index 01363914..ae7bd5a4 100644
--- a/test/samples/for-of.js
+++ b/test/samples/for-of.js
@@ -22,8 +22,8 @@ module.exports = [
 			}`,
 
 		output: `
-			for ( var i = 0, list = array; i < list.length; i += 1 ) {
-				var member = list[i];
+			for ( var i = 0, list = array, useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done; ) {
+				var member = useLen ? list[i++] : i.value;
 
 				doSomething( member );
 			}`
@@ -39,8 +39,8 @@ module.exports = [
 			}`,
 
 		output: `
-			for ( var i = 0, list = [ 'a', 'b', 'c' ]; i < list.length; i += 1 ) {
-				var member = list[i];
+			for ( var i = 0, list = [ 'a', 'b', 'c' ], useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done; ) {
+				var member = useLen ? list[i++] : i.value;
 
 				doSomething( member );
 			}`
@@ -59,14 +59,14 @@ module.exports = [
 
 		output: `
 			var loop = function () {
-				var member = list[i];
+				var member = useLen ? list[i++] : i.value;
 
 				setTimeout( function () {
 					doSomething( member );
 				});
 			};
 
-			for ( var i = 0, list = [ 'a', 'b', 'c' ]; i < list.length; i += 1 ) loop();`
+			for ( var i = 0, list = [ 'a', 'b', 'c' ], useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done; ) loop();`
 	},
 
 	{
@@ -77,8 +77,8 @@ module.exports = [
 			for ( let member of array ) console.log( member );`,
 
 		output: `
-			for ( var i = 0, list = array; i < list.length; i += 1 ) {
-				var member = list[i];
+			for ( var i = 0, list = array, useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done; ) {
+				var member = useLen ? list[i++] : i.value;
 
 				console.log( member );
 			}`
@@ -94,8 +94,8 @@ module.exports = [
 			}`,
 
 		output: `
-			for (var i = 0, list = this.keys; i < list.length; i += 1) {
-				var key = list[i];
+			for (var i = 0, list = this.keys, useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done;) {
+				var key = useLen ? list[i++] : i.value;
 
 				console.log(key);
 			}`
@@ -111,8 +111,8 @@ module.exports = [
 			}`,
 
 		output: `
-			for ( var i = 0, list = items; i < list.length; i += 1 ) {
-				var item = list[i];
+			for ( var i = 0, list = items, useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done; ) {
+				var item = useLen ? list[i++] : i.value;
 
 				if ( item.foo ) { continue; }
 			}`
@@ -136,7 +136,7 @@ module.exports = [
 			var this$1 = this;
 
 			var loop = function () {
-				var item = list[i];
+				var item = useLen ? list[i++] : i.value;
 
 				console.log( this$1, arguments$1, item );
 				setTimeout( function () {
@@ -144,7 +144,7 @@ module.exports = [
 				});
 			};
 
-			for ( var i = 0, list = items; i < list.length; i += 1 ) loop();`
+			for ( var i = 0, list = items, useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done; ) loop();`
 	},
 
 	{
@@ -187,7 +187,7 @@ module.exports = [
 		output: `
 			function foo () {
 				var loop = function () {
-					var x = list[i];
+					var x = useLen ? list[i++] : i.value;
 
 					setTimeout( function () {
 						console.log( x );
@@ -196,7 +196,7 @@ module.exports = [
 					if ( x > 10 ) { return {}; }
 				};
 
-				for ( var i = 0, list = y; i < list.length; i += 1 ) {
+				for ( var i = 0, list = y, useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done; ) {
 					var returned = loop();
 
 					if ( returned ) return returned.v;
@@ -214,8 +214,8 @@ module.exports = [
 			}`,
 
 		output: `
-			for (var i = 0, list = [{x: 1, y: 2}]; i < list.length; i += 1) {
-				var ref = list[i];
+			for (var i = 0, list = [{x: 1, y: 2}], useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done;) {
+				var ref = useLen ? list[i++] : i.value;
 				var x = ref.x;
 				var y = ref.y;
 
diff --git a/test/samples/loops.js b/test/samples/loops.js
index 10c4857c..4ef0cf54 100644
--- a/test/samples/loops.js
+++ b/test/samples/loops.js
@@ -504,8 +504,8 @@ module.exports = [
 		output: `
 			for (var a = 0; a < 10; a++) {
 				var j = 1, k = (void 0);
-				for (var i = 0, list = c; i < list.length; i += 1) {
-					var b = list[i];
+				for (var i = 0, list = c, useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done;) {
+					var b = useLen ? list[i++] : i.value;
 
 					var x = (void 0), y = 2
 					f(b, j, k, x, y)
@@ -526,8 +526,8 @@ module.exports = [
 			}
 		`,
 		output: `
-			for (var i = 0, list = c; i < list.length; i += 1) {
-				var b = list[i];
+			for (var i = 0, list = c, useLen = typeof list.length === 'number' || typeof Symbol !== 'function', list = useLen ? list : list[Symbol.iterator](); useLen ? i < list.length : !(i = list.next()).done;) {
+				var b = useLen ? list[i++] : i.value;
 
 				var x = (void 0), y = 2, z = (void 0);
 				f(b, x++, y++, z++)