diff --git a/lib/6to5/transformation/transform.js b/lib/6to5/transformation/transform.js
index 7a5a36fa77..4e2cd9379a 100644
--- a/lib/6to5/transformation/transform.js
+++ b/lib/6to5/transformation/transform.js
@@ -39,6 +39,8 @@ transform.moduleFormatters = {
 };
 
 _.each({
+  specNoForInOfAssignment:   require("./transformers/spec-no-for-in-of-assignment"),
+
   // playground
   methodBinding:             require("./transformers/playground-method-binding"),
   memoizationOperator:       require("./transformers/playground-memoization-operator"),
diff --git a/lib/6to5/transformation/transformers/spec-no-for-in-of-assignment.js b/lib/6to5/transformation/transformers/spec-no-for-in-of-assignment.js
new file mode 100644
index 0000000000..5af12108f1
--- /dev/null
+++ b/lib/6to5/transformation/transformers/spec-no-for-in-of-assignment.js
@@ -0,0 +1,10 @@
+var t = require("../../types");
+
+exports.ForInStatement =
+exports.ForOfStatement = function (node, parent, file) {
+  var left = node.left;
+  if (t.isVariableDeclaration(left)) {
+    var declar = left.declarations[0];
+    if (declar.init) throw file.errorWithNode(declar, "No assignments allowed in for-in/of head");
+  }
+};
diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index c291d12abd..85368e6f58 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -146,10 +146,10 @@ exports.template = function (name, nodes, keepExpression) {
   var node = template.body[0];
 
   if (!keepExpression && t.isExpressionStatement(node)) {
-    node = node.expression;
+    return node.expression;
+  } else {
+    return node;
   }
-
-  return node;
 };
 
 exports.codeFrame = function (lines, lineNumber, colNumber) {
diff --git a/test/fixtures/transformation/spec/for-in-assignment/actual.js b/test/fixtures/transformation/spec/for-in-assignment/actual.js
new file mode 100644
index 0000000000..167407a7da
--- /dev/null
+++ b/test/fixtures/transformation/spec/for-in-assignment/actual.js
@@ -0,0 +1,3 @@
+for (var i = 0 in obj) {
+
+}
diff --git a/test/fixtures/transformation/spec/for-in-assignment/options.json b/test/fixtures/transformation/spec/for-in-assignment/options.json
new file mode 100644
index 0000000000..c7ae9b8aa4
--- /dev/null
+++ b/test/fixtures/transformation/spec/for-in-assignment/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "No assignments allowed in for-in/of head"
+}
diff --git a/test/fixtures/transformation/spec/for-of-assignment/actual.js b/test/fixtures/transformation/spec/for-of-assignment/actual.js
new file mode 100644
index 0000000000..56e4dfef82
--- /dev/null
+++ b/test/fixtures/transformation/spec/for-of-assignment/actual.js
@@ -0,0 +1,3 @@
+for (var i = 0 of obj) {
+
+}
diff --git a/test/fixtures/transformation/spec/for-of-assignment/options.json b/test/fixtures/transformation/spec/for-of-assignment/options.json
new file mode 100644
index 0000000000..c7ae9b8aa4
--- /dev/null
+++ b/test/fixtures/transformation/spec/for-of-assignment/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "No assignments allowed in for-in/of head"
+}