diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index 79479363acd..b46d44c5982 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -548,11 +548,6 @@ def typeIsSequenceOrHasSequenceMember(type):
     return False
 
 
-def typeNeedsRooting(type, descriptorProvider):
-    return (type.isGeckoInterface() and
-            descriptorProvider.getDescriptor(type.unroll().inner.identifier.name).needsRooting)
-
-
 def union_native_type(t):
     name = t.unroll().name
     return 'UnionTypes::%s' % name
@@ -1422,8 +1417,6 @@ def getRetvalDeclarationForType(returnType, descriptorProvider):
         nullable = returnType.nullable()
         dictName = returnType.inner.name if nullable else returnType.name
         result = CGGeneric(dictName)
-        if typeNeedsRooting(returnType, descriptorProvider):
-            raise TypeError("We don't support rootable dictionaries return values")
         if nullable:
             result = CGWrapper(result, pre="Option<", post=">")
         return result
@@ -6122,14 +6115,19 @@ class CGBindingRoot(CGThing):
 
         # Do codegen for all the typdefs
         for t in typedefs:
-            if t.innerType.isUnion():
-                cgthings.extend([CGGeneric("\npub use dom::bindings::codegen::UnionTypes::%s as %s;\n\n" %
-                                           (t.innerType, t.identifier.name))])
+            typeName = getRetvalDeclarationForType(t.innerType, config.getDescriptorProvider())
+            substs = {
+                "name": t.identifier.name,
+                "type": typeName.define(),
+            }
+
+            if t.innerType.isUnion() and not t.innerType.nullable():
+                # Allow using the typedef's name for accessing variants.
+                template = "pub use self::%(type)s as %(name)s;"
             else:
-                assert not typeNeedsRooting(t.innerType, config.getDescriptorProvider)
-                cgthings.extend([CGGeneric("\npub type %s = " % (t.identifier.name)),
-                                 getRetvalDeclarationForType(t.innerType, config.getDescriptorProvider()),
-                                 CGGeneric(";\n\n")])
+                template = "pub type %(name)s = %(type)s;"
+
+            cgthings.append(CGGeneric(template % substs))
 
         # Do codegen for all the dictionaries.
         cgthings.extend([CGDictionary(d, config.getDescriptorProvider())
diff --git a/components/script/dom/bindings/codegen/Configuration.py b/components/script/dom/bindings/codegen/Configuration.py
index 14a11c139a9..0fe9bf6c004 100644
--- a/components/script/dom/bindings/codegen/Configuration.py
+++ b/components/script/dom/bindings/codegen/Configuration.py
@@ -201,20 +201,17 @@ class Descriptor(DescriptorProvider):
         # Callback and SpiderMonkey types do not use JS smart pointers, so we should not use the
         # built-in rooting mechanisms for them.
         if spiderMonkeyInterface:
-            self.needsRooting = False
             self.returnType = 'Rc<%s>' % typeName
             self.argumentType = '&%s' % typeName
             self.nativeType = typeName
             pathDefault = 'dom::types::%s' % typeName
         elif self.interface.isCallback():
-            self.needsRooting = False
             ty = 'dom::bindings::codegen::Bindings::%sBinding::%s' % (ifaceName, ifaceName)
             pathDefault = ty
             self.returnType = "Rc<%s>" % ty
             self.argumentType = "???"
             self.nativeType = ty
         else:
-            self.needsRooting = True
             self.returnType = "Root<%s>" % typeName
             self.argumentType = "&%s" % typeName
             self.nativeType = "*const %s" % typeName
diff --git a/components/script/dom/webidls/TestBinding.webidl b/components/script/dom/webidls/TestBinding.webidl
index 6920ded6301..fc6d4771366 100644
--- a/components/script/dom/webidls/TestBinding.webidl
+++ b/components/script/dom/webidls/TestBinding.webidl
@@ -7,6 +7,9 @@
 
 enum TestEnum { "", "foo", "bar" };
 typedef (DOMString or URL or Blob) TestTypedef;
+typedef (DOMString or URL or Blob)? TestTypedefNullableUnion;
+typedef DOMString TestTypedefString;
+typedef Blob TestTypedefInterface;
 
 dictionary TestDictionary {
   required boolean requiredValue;