diff --git a/fpdfsdk/include/javascript/JS_Runtime.h b/fpdfsdk/include/javascript/JS_Runtime.h
index f4dabf0..3be0f76 100644
--- a/fpdfsdk/include/javascript/JS_Runtime.h
+++ b/fpdfsdk/include/javascript/JS_Runtime.h
@@ -68,6 +68,7 @@
   CJS_FieldEvent* m_pFieldEventPath;
 
   v8::Isolate* m_isolate;
+  bool m_isolateManaged;
   nonstd::unique_ptr<CJS_ArrayBufferAllocator> m_pArrayBufferAllocator;
   v8::Global<v8::Context> m_context;
 };
diff --git a/fpdfsdk/src/javascript/JS_Runtime.cpp b/fpdfsdk/src/javascript/JS_Runtime.cpp
index 08cd87c..4ef34a8 100644
--- a/fpdfsdk/src/javascript/JS_Runtime.cpp
+++ b/fpdfsdk/src/javascript/JS_Runtime.cpp
@@ -98,7 +98,8 @@
       m_pDocument(NULL),
       m_bBlocking(FALSE),
       m_pFieldEventPath(NULL),
-      m_isolate(NULL) {
+      m_isolate(NULL),
+      m_isolateManaged(false) {
   if (m_pApp->GetFormFillInfo()->m_pJsPlatform->version >= 2) {
     m_isolate = reinterpret_cast<v8::Isolate*>(
         m_pApp->GetFormFillInfo()->m_pJsPlatform->m_isolate);
@@ -109,6 +110,7 @@
     v8::Isolate::CreateParams params;
     params.array_buffer_allocator = m_pArrayBufferAllocator.get();
     m_isolate = v8::Isolate::New(params);
+    m_isolateManaged = true;
   }
 
   InitJSObjects();
@@ -133,8 +135,8 @@
   m_pFieldEventPath = NULL;
   m_context.Reset();
 
-  // m_isolate->Exit();
-  m_isolate->Dispose();
+  if (m_isolateManaged)
+    m_isolate->Dispose();
 }
 
 FX_BOOL CJS_Runtime::InitJSObjects() {