diff --git a/lib/6to5/generation/generators/expressions.js b/lib/6to5/generation/generators/expressions.js
index 17f5dbda68..ea767f86a4 100644
--- a/lib/6to5/generation/generators/expressions.js
+++ b/lib/6to5/generation/generators/expressions.js
@@ -116,3 +116,8 @@ exports.MemberExpression = function (node, print) {
     print(node.property);
   }
 };
+
+exports.TypeOfExpression = function (node, print) {
+  this.push("typeof ");
+  print(node.expression);
+};
diff --git a/lib/6to5/types/alias-keys.json b/lib/6to5/types/alias-keys.json
index 56ad154225..ae414db878 100644
--- a/lib/6to5/types/alias-keys.json
+++ b/lib/6to5/types/alias-keys.json
@@ -1,5 +1,6 @@
 {
   "ExpressionStatement": ["Statement"],
+  "TypeOfExpression":    ["Statement"],
   "BreakStatement":      ["Statement"],
   "ContinueStatement":   ["Statement"],
   "DebuggerStatement":   ["Statement"],
diff --git a/lib/6to5/types/builder-keys.json b/lib/6to5/types/builder-keys.json
index e9ac7987be..d5836d6bcb 100644
--- a/lib/6to5/types/builder-keys.json
+++ b/lib/6to5/types/builder-keys.json
@@ -7,6 +7,7 @@
   "CallExpression":          ["callee", "arguments"],
   "ConditionalExpression":   ["test", "consequent", "alternate"],
   "ExpressionStatement":     ["expression"],
+  "TypeOfExpression":        ["expression"],
   "File":                    ["program", "comments", "tokens"],
   "FunctionExpression":      ["id", "params", "body", "generator"],
   "Identifier":              ["name"],
diff --git a/lib/6to5/types/visitor-keys.json b/lib/6to5/types/visitor-keys.json
index 32292aa669..7a963a8faf 100644
--- a/lib/6to5/types/visitor-keys.json
+++ b/lib/6to5/types/visitor-keys.json
@@ -26,6 +26,7 @@
   "ExportDeclaration":         ["declaration", "specifiers", "source"],
   "ExportSpecifier":           ["id", "name"],
   "ExpressionStatement":       ["expression"],
+  "TypeOfExpression":          ["expression"],
   "File":                      ["program"],
   "ForInStatement":            ["left", "right", "body"],
   "ForOfStatement":            ["left", "right", "body"],