diff --git a/fxjs/fxjs_v8.cpp b/fxjs/fxjs_v8.cpp
index 5304254..ebe38fd 100644
--- a/fxjs/fxjs_v8.cpp
+++ b/fxjs/fxjs_v8.cpp
@@ -219,6 +219,8 @@
 
 CFXJS_Engine::CFXJS_Engine() : m_isolate(nullptr) {}
 
+CFXJS_Engine::CFXJS_Engine(v8::Isolate* pIsolate) : m_isolate(pIsolate) {}
+
 CFXJS_Engine::~CFXJS_Engine() {
   m_V8PersistentContext.Reset();
 }
diff --git a/fxjs/fxjs_v8_embeddertest.cpp b/fxjs/fxjs_v8_embeddertest.cpp
index 2da3131..a877a36 100644
--- a/fxjs/fxjs_v8_embeddertest.cpp
+++ b/fxjs/fxjs_v8_embeddertest.cpp
@@ -45,12 +45,10 @@
   v8::Isolate::Scope isolate_scope(isolate());
   v8::HandleScope handle_scope(isolate());
 
-  CFXJS_Engine engine1;
-  engine1.SetIsolate(isolate());
+  CFXJS_Engine engine1(isolate());
   engine1.InitializeEngine();
 
-  CFXJS_Engine engine2;
-  engine2.SetIsolate(isolate());
+  CFXJS_Engine engine2(isolate());
   engine2.InitializeEngine();
 
   v8::Context::Scope context_scope(GetV8Context());
diff --git a/fxjs/include/fxjs_v8.h b/fxjs/include/fxjs_v8.h
index c08cc8b..8b5fc83 100644
--- a/fxjs/include/fxjs_v8.h
+++ b/fxjs/include/fxjs_v8.h
@@ -138,7 +138,7 @@
 
 class CFXJS_Engine {
  public:
-  CFXJS_Engine();
+  explicit CFXJS_Engine(v8::Isolate* pIsolate);
   ~CFXJS_Engine();
 
   using Constructor = void (*)(CFXJS_Engine* pEngine,
@@ -155,8 +155,6 @@
                               CFXJS_Engine* pEngine);
 #endif  // PDF_ENABLE_XFA
 
-  // TODO(tsepez): to constructor.
-  void SetIsolate(v8::Isolate* pIsolate) { m_isolate = pIsolate; }
   v8::Isolate* GetIsolate() const { return m_isolate; }
 
   // Always returns a valid, newly-created objDefnID.
@@ -258,6 +256,11 @@
   v8::Local<v8::String> WSToJSString(const CFX_WideString& wsPropertyName);
   void Error(const CFX_WideString& message);
 
+ protected:
+  CFXJS_Engine();
+
+  void SetIsolate(v8::Isolate* pIsolate) { m_isolate = pIsolate; }
+
  private:
   v8::Isolate* m_isolate;
   v8::Global<v8::Context> m_V8PersistentContext;
diff --git a/testing/js_embedder_test.cpp b/testing/js_embedder_test.cpp
index f7aa7e3..125d2bf 100644
--- a/testing/js_embedder_test.cpp
+++ b/testing/js_embedder_test.cpp
@@ -21,8 +21,7 @@
   v8::Isolate::Scope isolate_scope(m_pIsolate);
   v8::HandleScope handle_scope(m_pIsolate);
   FXJS_PerIsolateData::SetUp(m_pIsolate);
-  m_Engine.reset(new CFXJS_Engine);
-  m_Engine->SetIsolate(m_pIsolate);
+  m_Engine.reset(new CFXJS_Engine(m_pIsolate));
   m_Engine->InitializeEngine();
 }