diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index 79479363acd..e5c3761edfe 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -6122,7 +6122,8 @@ class CGBindingRoot(CGThing):
 
         # Do codegen for all the typdefs
         for t in typedefs:
-            if t.innerType.isUnion():
+            if t.innerType.isUnion() and not t.innerType.nullable():
+                # Allow using the typedef's name for accessing variants.
                 cgthings.extend([CGGeneric("\npub use dom::bindings::codegen::UnionTypes::%s as %s;\n\n" %
                                            (t.innerType, t.identifier.name))])
             else:
diff --git a/components/script/dom/webidls/TestBinding.webidl b/components/script/dom/webidls/TestBinding.webidl
index 6920ded6301..59d4fb35466 100644
--- a/components/script/dom/webidls/TestBinding.webidl
+++ b/components/script/dom/webidls/TestBinding.webidl
@@ -7,6 +7,7 @@
 
 enum TestEnum { "", "foo", "bar" };
 typedef (DOMString or URL or Blob) TestTypedef;
+typedef (DOMString or URL or Blob)? TestTypedefNullableUnion;
 
 dictionary TestDictionary {
   required boolean requiredValue;