diff --git a/ets2panda/checker/types/ets/etsNullishTypes.cpp b/ets2panda/checker/types/ets/etsNullishTypes.cpp
index 6e102e16751ae3c4b039af93f2d5a8278a34a2de..e9abc5839f4d6d494453c5aa8d7ad9fab029c3b0 100644
--- a/ets2panda/checker/types/ets/etsNullishTypes.cpp
+++ b/ets2panda/checker/types/ets/etsNullishTypes.cpp
@@ -59,12 +59,12 @@ void ETSNullType::ToString(std::stringstream &ss, [[maybe_unused]] bool precise)
 
 void ETSNullType::ToAssemblerType(std::stringstream &ss) const
 {
-    ss << compiler::Signatures::BUILTIN_OBJECT;
+    ss << compiler::Signatures::NULL_ASSEMBLY_TYPE;
 }
 
 void ETSNullType::ToDebugInfoType(std::stringstream &ss) const
 {
-    ss << ETSObjectType::NameToDescriptor(compiler::Signatures::BUILTIN_OBJECT);
+    ss << ETSObjectType::NameToDescriptor(compiler::Signatures::NULL_ASSEMBLY_TYPE);
 }
 
 Type *ETSNullType::Instantiate([[maybe_unused]] ArenaAllocator *allocator, [[maybe_unused]] TypeRelation *relation,
diff --git a/ets2panda/test/unit/union_emit_test.cpp b/ets2panda/test/unit/union_emit_test.cpp
index 47134d0b4f4334d4d2d230d68aca808426e9e267..13fcd11f6dc862ada91276bff2eb572405887db1 100644
--- a/ets2panda/test/unit/union_emit_test.cpp
+++ b/ets2panda/test/unit/union_emit_test.cpp
@@ -24,6 +24,16 @@ public:
 
     ~UnionAsmTest() override = default;
 
+    void CheckFunction(std::string_view funcSig, bool found = true)
+    {
+        pandasm::Function *func = GetFunction(funcSig, program_->functionStaticTable);
+        if (found) {
+            ASSERT_TRUE(func != nullptr) << "Function '" << funcSig << "' not found";
+        } else {
+            ASSERT_TRUE(func == nullptr) << "Function '" << funcSig << "' found";
+        }
+    }
+
     void CheckUnionType(std::string_view recordName, bool found = true)
     {
         pandasm::Record *rec = GetRecord(recordName, program_);
@@ -234,4 +244,19 @@ TEST_F(UnionAsmTest, union_test_as)
     CheckInsInFunction("dummy.ETSGLOBAL.test1:std.core.String;void;", "std.core.Runtime.failedTypeCastException", true);
 }
 
+TEST_F(UnionAsmTest, union_null_object)
+{
+    SetCurrentProgram(R"(
+        type T1 = string | null | undefined | object
+        type T2 = string | object | null | undefined
+        function foo1(a: T1) {}
+        function foo2(a: T2) {}
+    )");
+
+    CheckFunction("dummy.ETSGLOBAL.foo1:{Ustd.core.Null,std.core.Object};void;");
+    CheckFunction("dummy.ETSGLOBAL.foo2:{Ustd.core.Null,std.core.Object};void;");
+    CheckFunction("dummy.ETSGLOBAL.foo1:std.core.Object;void;", false);
+    CheckFunction("dummy.ETSGLOBAL.foo2:std.core.Object;void;", false);
+}
+
 }  // namespace ark::es2panda::compiler::test