diff --git a/src/node_builtins.cc b/src/node_builtins.cc
index d6b5114aa3c4aa..46a52e301efeb0 100644
--- a/src/node_builtins.cc
+++ b/src/node_builtins.cc
@@ -32,8 +32,6 @@ using v8::String;
 using v8::Undefined;
 using v8::Value;
 
-BuiltinLoader BuiltinLoader::instance_;
-
 BuiltinLoader::BuiltinLoader() : config_(GetConfig()), has_code_cache_(false) {
   LoadJavaScriptSource();
 #ifdef NODE_SHARED_BUILTIN_CJS_MODULE_LEXER_LEXER_PATH
@@ -55,6 +53,7 @@ BuiltinLoader::BuiltinLoader() : config_(GetConfig()), has_code_cache_(false) {
 }
 
 BuiltinLoader* BuiltinLoader::GetInstance() {
+  static BuiltinLoader instance_;
   return &instance_;
 }
 
@@ -63,8 +62,11 @@ bool BuiltinLoader::Exists(const char* id) {
   return source.find(id) != source.end();
 }
 
-bool BuiltinLoader::Add(const char* id, const UnionBytes& source) {
-  auto result = GetInstance()->source_.emplace(id, source);
+bool BuiltinLoader::Add(const char* id,
+                        const UnionBytes& source,
+                        BuiltinLoader* instance) {
+  if (instance == nullptr) instance = GetInstance();
+  auto result = instance->source_.emplace(id, source);
   return result.second;
 }
 
@@ -249,10 +251,12 @@ void BuiltinLoader::AddExternalizedBuiltin(const char* id,
     ABORT();
   }
 
-  Add(id, source);
+  Add(id, source, this);
 }
 
-bool BuiltinLoader::Add(const char* id, std::string_view utf8source) {
+bool BuiltinLoader::Add(const char* id,
+                        std::string_view utf8source,
+                        BuiltinLoader* instance) {
   size_t expected_u16_length =
       simdutf::utf16_length_from_utf8(utf8source.data(), utf8source.length());
   auto out = std::make_shared<std::vector<uint16_t>>(expected_u16_length);
@@ -261,7 +265,7 @@ bool BuiltinLoader::Add(const char* id, std::string_view utf8source) {
       utf8source.length(),
       reinterpret_cast<char16_t*>(out->data()));
   out->resize(u16_length);
-  return Add(id, UnionBytes(out));
+  return Add(id, UnionBytes(out), instance);
 }
 
 // Returns Local<Function> of the compiled module if return_code_cache
diff --git a/src/node_builtins.h b/src/node_builtins.h
index f90a4151850d54..ec8bff22f661b1 100644
--- a/src/node_builtins.h
+++ b/src/node_builtins.h
@@ -67,8 +67,14 @@ class NODE_EXTERN_PRIVATE BuiltinLoader {
   // Returns config.gypi as a JSON string
   static v8::Local<v8::String> GetConfigString(v8::Isolate* isolate);
   static bool Exists(const char* id);
-  static bool Add(const char* id, const UnionBytes& source);
-  static bool Add(const char* id, std::string_view utf8source);
+  // TODO(addaleax): Make BuiltinLoader non-global so that these
+  // methods do not need to be static.
+  static bool Add(const char* id,
+                  const UnionBytes& source,
+                  BuiltinLoader* instance = nullptr);
+  static bool Add(const char* id,
+                  std::string_view utf8source,
+                  BuiltinLoader* instance = nullptr);
 
   static bool CompileAllBuiltins(v8::Local<v8::Context> context);
   static void RefreshCodeCache(const std::vector<CodeCacheInfo>& in);
@@ -134,9 +140,8 @@ class NODE_EXTERN_PRIVATE BuiltinLoader {
   static void HasCachedBuiltins(
       const v8::FunctionCallbackInfo<v8::Value>& args);
 
-  static void AddExternalizedBuiltin(const char* id, const char* filename);
+  void AddExternalizedBuiltin(const char* id, const char* filename);
 
-  static BuiltinLoader instance_;
   BuiltinCategories builtin_categories_;
   BuiltinSourceMap source_;
   BuiltinCodeCacheMap code_cache_;
diff --git a/test/cctest/test_per_process.cc b/test/cctest/test_per_process.cc
index 1e3dff7114e337..f5bbeca5e4dd17 100644
--- a/test/cctest/test_per_process.cc
+++ b/test/cctest/test_per_process.cc
@@ -11,7 +11,7 @@ using node::builtins::BuiltinSourceMap;
 class PerProcessTest : public ::testing::Test {
  protected:
   static const BuiltinSourceMap get_sources_for_test() {
-    return BuiltinLoader::instance_.source_;
+    return BuiltinLoader::GetInstance()->source_;
   }
 };