diff --git a/src/components/script/dom/bindings/codegen/CodegenRust.py b/src/components/script/dom/bindings/codegen/CodegenRust.py
index 2110ab7ebd9..9df2e31649a 100644
--- a/src/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/src/components/script/dom/bindings/codegen/CodegenRust.py
@@ -751,11 +751,11 @@ def getJSToNativeConversionTemplate(type, descriptorProvider, failureCode=None,
 
         if defaultValue is not None:
             assert(defaultValue.type.tag() == IDLType.Tags.domstring)
-            template = "" #XXXjdm unfinished
-            #template = handleDefault(template,
-            #                         ("${declName} = %sValues::%s;" %
-            #                          (enum,
-            #                           getEnumValueName(defaultValue.value))))
+            template = handleDefault(template,
+                                     ("${declName} = %sValues::%s;" %
+                                      (enum,
+                                       getEnumValueName(defaultValue.value))))
+
         return (template, CGGeneric(enum), None, isOptional, None)
 
     if type.isCallback():
diff --git a/src/components/script/dom/testbinding.rs b/src/components/script/dom/testbinding.rs
index 53dbced8c36..363db6e0ee0 100644
--- a/src/components/script/dom/testbinding.rs
+++ b/src/components/script/dom/testbinding.rs
@@ -120,7 +120,7 @@ impl TestBinding {
     pub fn PassOptionalLongLongWithDefault(&self, _: i64) {}
     pub fn PassOptionalUnsignedLongLongWithDefault(&self, _: u64) {}
     pub fn PassOptionalStringWithDefault(&self, _: DOMString) {}
-    // pub fn PassOptionalEnumWithDefault(&self, _: TestEnum) {}
+    pub fn PassOptionalEnumWithDefault(&self, _: TestEnum) {}
 
     pub fn PassOptionalNullableBooleanWithDefault(&self, _: Option<bool>) {}
     pub fn PassOptionalNullableByteWithDefault(&self, _: Option<i8>) {}
diff --git a/src/components/script/dom/webidls/TestBinding.webidl b/src/components/script/dom/webidls/TestBinding.webidl
index 93196cf8e3c..56f54bb461b 100644
--- a/src/components/script/dom/webidls/TestBinding.webidl
+++ b/src/components/script/dom/webidls/TestBinding.webidl
@@ -77,7 +77,7 @@ interface TestBinding {
   void passOptionalLongLongWithDefault(optional long long arg = -12);
   void passOptionalUnsignedLongLongWithDefault(optional unsigned long long arg = 17);
   void passOptionalStringWithDefault(optional DOMString arg = "");
-  // void passOptionalEnumWithDefault(optional TestEnum arg = "foo");
+  void passOptionalEnumWithDefault(optional TestEnum arg = "foo");
 
   void passOptionalNullableBooleanWithDefault(optional boolean? arg = null);
   void passOptionalNullableByteWithDefault(optional byte? arg = null);