diff --git a/lib/6to5/transformation/transform.js b/lib/6to5/transformation/transform.js
index e40af5089f..02e0d3cfe7 100644
--- a/lib/6to5/transformation/transform.js
+++ b/lib/6to5/transformation/transform.js
@@ -81,6 +81,7 @@ _.each({
   _declarations:             require("./transformers/_declarations"),
 
   coreAliasing:              require("./transformers/optional-core-aliasing"),
+  undefinedToVoid:           require("./transformers/optional-undefined-to-void"),
 
   // wrap up
   _aliasFunctions:           require("./transformers/_alias-functions"),
diff --git a/test/fixtures/transformation/optional-undefined-to-void/basic/actual.js b/test/fixtures/transformation/optional-undefined-to-void/basic/actual.js
new file mode 100644
index 0000000000..cbe08826de
--- /dev/null
+++ b/test/fixtures/transformation/optional-undefined-to-void/basic/actual.js
@@ -0,0 +1,2 @@
+var foo;
+foo === undefined;
diff --git a/test/fixtures/transformation/optional-undefined-to-void/basic/expected.js b/test/fixtures/transformation/optional-undefined-to-void/basic/expected.js
new file mode 100644
index 0000000000..1ce44e235f
--- /dev/null
+++ b/test/fixtures/transformation/optional-undefined-to-void/basic/expected.js
@@ -0,0 +1,4 @@
+"use strict";
+
+var foo;
+foo === void 0;
diff --git a/test/fixtures/transformation/optional-undefined-to-void/member-expression/actual.js b/test/fixtures/transformation/optional-undefined-to-void/member-expression/actual.js
new file mode 100644
index 0000000000..ca34d86226
--- /dev/null
+++ b/test/fixtures/transformation/optional-undefined-to-void/member-expression/actual.js
@@ -0,0 +1,2 @@
+var foo;
+foo === undefined.foo;
diff --git a/test/fixtures/transformation/optional-undefined-to-void/member-expression/expected.js b/test/fixtures/transformation/optional-undefined-to-void/member-expression/expected.js
new file mode 100644
index 0000000000..866a1bf53e
--- /dev/null
+++ b/test/fixtures/transformation/optional-undefined-to-void/member-expression/expected.js
@@ -0,0 +1,4 @@
+"use strict";
+
+var foo;
+foo === (void 0).foo;
diff --git a/test/fixtures/transformation/optional-undefined-to-void/options.json b/test/fixtures/transformation/optional-undefined-to-void/options.json
new file mode 100644
index 0000000000..951ad97b89
--- /dev/null
+++ b/test/fixtures/transformation/optional-undefined-to-void/options.json
@@ -0,0 +1,3 @@
+{
+  "optional": ["undefinedToVoid"]
+}