diff --git a/src/components/script/dom/bindings/codegen/CodegenRust.py b/src/components/script/dom/bindings/codegen/CodegenRust.py
index ed70d7a1ecb..a161dbc54ee 100644
--- a/src/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/src/components/script/dom/bindings/codegen/CodegenRust.py
@@ -4119,7 +4119,9 @@ class CGDictionary(CGThing):
         return "/* uh oh */ %s" % name
 
     def getMemberType(self, memberInfo):
-        _, (_, _, declType, _) = memberInfo
+        member, (_, _, declType, _) = memberInfo
+        if not member.defaultValue:
+            declType = CGWrapper(declType, pre="Option<", post=">")
         return declType.define()
 
     def getMemberConversion(self, memberInfo):
@@ -4127,12 +4129,14 @@ class CGDictionary(CGThing):
             return CGIndenter(CGGeneric(s), 8).define()
 
         member, (templateBody, default, declType, _) = memberInfo
-        if not member.defaultValue:
-            raise TypeError("We don't support dictionary members without a "
-                            "default value.")
-
         replacements = { "val": "value" }
         conversion = string.Template(templateBody).substitute(replacements)
+
+        assert (member.defaultValue is None) == (default is None)
+        if not default:
+            default = "None"
+            conversion = "Some(%s)" % conversion
+
         conversion = (
             "match get_dictionary_property(cx, object, \"%s\") {\n"
             "    Err(()) => return Err(()),\n"
diff --git a/src/components/script/dom/webidls/TestBinding.webidl b/src/components/script/dom/webidls/TestBinding.webidl
index 578a2d3948b..e2e45b03c83 100644
--- a/src/components/script/dom/webidls/TestBinding.webidl
+++ b/src/components/script/dom/webidls/TestBinding.webidl
@@ -4,23 +4,23 @@
 
 enum TestEnum { "", "foo", "bar" };
 
-/* dictionary TestDictionary {
-  // boolean booleanValue;
-  // byte byteValue;
-  // octet octetValue;
-  // short shortValue;
-  // unsigned short unsignedShortValue;
-  // long longValue;
-  // unsigned long unsignedLongValue;
-  // long long longLongValue;
-  // unsigned long long unsignedLongLongValue;
-  // float floatValue;
-  // double doubleValue;
-  // DOMString stringValue;
-  // TestEnum enumValue;
-  // Blob interfaceValue;
-  // any anyValue;
-}; */
+dictionary TestDictionary {
+  boolean booleanValue;
+  byte byteValue;
+  octet octetValue;
+  short shortValue;
+  unsigned short unsignedShortValue;
+  long longValue;
+  unsigned long unsignedLongValue;
+  long long longLongValue;
+  unsigned long long unsignedLongLongValue;
+  float floatValue;
+  double doubleValue;
+  DOMString stringValue;
+  TestEnum enumValue;
+  Blob interfaceValue;
+  any anyValue;
+};
 
 dictionary TestDictionaryDefaults {
   boolean booleanValue = false;