diff --git a/lib/6to5/transformation/transform.js b/lib/6to5/transformation/transform.js
index a1c7a104ac..4c64371d3a 100644
--- a/lib/6to5/transformation/transform.js
+++ b/lib/6to5/transformation/transform.js
@@ -80,13 +80,12 @@ _.each({
   constants:                 require("./transformers/es6-constants"),
   letScoping:                require("./transformers/es6-let-scoping"),
 
-  _blockHoist:               require("./transformers/_block-hoist"),
-
   generators:                require("./transformers/es6-generators"),
   restParameters:            require("./transformers/es6-rest-parameters"),
 
   protoToAssign:             require("./transformers/optional-proto-to-assign"),
 
+  _blockHoist:               require("./transformers/_block-hoist"),
   _declarations:             require("./transformers/_declarations"),
 
   // wrap up
@@ -97,6 +96,7 @@ _.each({
   typeofSymbol:              require("./transformers/optional-typeof-symbol"),
   externalRuntime:           require("./transformers/optional-external-runtime"),
   coreAliasing:              require("./transformers/optional-core-aliasing"),
+  externalRegenerator:       require("./transformers/optional-external-regenerator-runtime"),
   undefinedToVoid:           require("./transformers/optional-undefined-to-void"),
 
   // spec
diff --git a/lib/6to5/transformation/transformers/optional-external-regenerator-runtime.js b/lib/6to5/transformation/transformers/optional-external-regenerator-runtime.js
new file mode 100644
index 0000000000..9294a6c76e
--- /dev/null
+++ b/lib/6to5/transformation/transformers/optional-external-regenerator-runtime.js
@@ -0,0 +1,16 @@
+var t = require("../../types");
+
+exports.optional = true;
+
+exports.ast = {
+  enter: function (ast, file) {
+    file._regeneratorId = file.addImport("regenerator/runtime-module", "regeneratorRuntime");
+  }
+};
+
+exports.MemberExpression = function (node, parent, scope, context, file) {
+  var obj = node.object;
+  var prop = node.property;
+  if (!t.isReferenced(node, parent) || !t.isReferenced(obj, node)) return;
+  if (obj.name === "regeneratorRuntime") return t.memberExpression(file._regeneratorId, prop);
+};
diff --git a/test/fixtures/transformation/optional-external-regenerator-runtime/basic/actual.js b/test/fixtures/transformation/optional-external-regenerator-runtime/basic/actual.js
new file mode 100644
index 0000000000..ae6cc4d8c8
--- /dev/null
+++ b/test/fixtures/transformation/optional-external-regenerator-runtime/basic/actual.js
@@ -0,0 +1,2 @@
+void function* () {
+};
diff --git a/test/fixtures/transformation/optional-external-regenerator-runtime/basic/expected.js b/test/fixtures/transformation/optional-external-regenerator-runtime/basic/expected.js
new file mode 100644
index 0000000000..00320c54b6
--- /dev/null
+++ b/test/fixtures/transformation/optional-external-regenerator-runtime/basic/expected.js
@@ -0,0 +1,13 @@
+"use strict";
+
+var _regeneratorRuntime = require("regenerator/runtime-module");
+
+void _regeneratorRuntime.mark(function callee$0$0() {
+  return _regeneratorRuntime.wrap(function callee$0$0$(context$1$0) {
+    while (1) switch (context$1$0.prev = context$1$0.next) {
+      case 0:
+      case "end":
+        return context$1$0.stop();
+    }
+  }, callee$0$0, this);
+});
diff --git a/test/fixtures/transformation/optional-external-regenerator-runtime/options.json b/test/fixtures/transformation/optional-external-regenerator-runtime/options.json
new file mode 100644
index 0000000000..40d336b5be
--- /dev/null
+++ b/test/fixtures/transformation/optional-external-regenerator-runtime/options.json
@@ -0,0 +1,3 @@
+{
+  "optional": ["externalRegenerator"]
+}