diff --git a/ReactCommon/cxxreact/BUCK b/ReactCommon/cxxreact/BUCK
index efcf46c40..f2df12617 100644
--- a/ReactCommon/cxxreact/BUCK
+++ b/ReactCommon/cxxreact/BUCK
@@ -133,7 +133,7 @@ react_library(
   soname = 'libreactnativefb.$(ext)',
   header_namespace = 'cxxreact',
   force_static = True,
-  srcs = glob(['*.cpp']),
+  srcs = glob(['*.cpp'], excludes=['SampleCxxModule.cpp']),
   headers = glob(['*.h'], excludes=CXXREACT_PUBLIC_HEADERS),
   xcode_public_headers_symlinks = True,
   exported_headers = CXXREACT_PUBLIC_HEADERS,
diff --git a/ReactCommon/cxxreact/JSCExecutor.cpp b/ReactCommon/cxxreact/JSCExecutor.cpp
index acfeaa79e..f3a557b8b 100644
--- a/ReactCommon/cxxreact/JSCExecutor.cpp
+++ b/ReactCommon/cxxreact/JSCExecutor.cpp
@@ -209,8 +209,8 @@ void JSCExecutor::destroy() {
 }
 
 void JSCExecutor::setContextName(const std::string& name) {
-  String jsName = String(name.c_str());
-  JSGlobalContextSetName(m_context, static_cast<JSStringRef>(jsName));
+  String jsName = String(m_context, name.c_str());
+  JSGlobalContextSetName(m_context, jsName);
 }
 
 void JSCExecutor::initOnJSVMThread() throw(JSException) {
@@ -313,7 +313,7 @@ void JSCExecutor::loadApplicationScript(
     (flags & UNPACKED_JS_SOURCE) || (flags & UNPACKED_BYTECODE),
     "Optimized bundle with no unpacked source or bytecode");
 
-  String jsSourceURL(sourceURL.c_str());
+  String jsSourceURL(m_context, sourceURL.c_str());
   JSSourceCodeRef sourceCode = nullptr;
   SCOPE_EXIT {
     if (sourceCode) {
@@ -338,9 +338,11 @@ void JSCExecutor::loadApplicationScript(
       return loadApplicationScript(std::move(jsScriptBigString), sourceURL);
     }
 
+    #if defined(WITH_FB_JSC_TUNING) && defined(__ANDROID__)
     if (flags & UNPACKED_BC_CACHE) {
       configureJSCBCCache(m_context, bundlePath);
     }
+    #endif
 
     sourceCode = JSCreateSourceCode(
       jsScriptBigString->fd(),
@@ -403,14 +405,14 @@ void JSCExecutor::loadApplicationScript(std::unique_ptr<const JSBigString> scrip
   ReactMarker::logMarker("RUN_JS_BUNDLE_START");
 
   ReactMarker::logMarker("loadApplicationScript_startStringConvert");
-  String jsScript = jsStringFromBigString(*script);
+  String jsScript = jsStringFromBigString(m_context, *script);
   ReactMarker::logMarker("loadApplicationScript_endStringConvert");
 
   #ifdef WITH_FBSYSTRACE
   fbsystrace_end_section(TRACE_TAG_REACT_CXX_BRIDGE);
   #endif
 
-  String jsSourceURL(sourceURL.c_str());
+  String jsSourceURL(m_context, sourceURL.c_str());
   evaluateScript(m_context, jsScript, jsSourceURL);
 
   // TODO(luk): t13903306 Remove this check once we make native modules working for java2js
@@ -473,8 +475,8 @@ void JSCExecutor::callFunction(const std::string& moduleId, const std::string& m
   auto result = [&] {
     try {
       return m_callFunctionReturnFlushedQueueJS->callAsFunction({
-        Value(m_context, String::createExpectingAscii(moduleId)),
-        Value(m_context, String::createExpectingAscii(methodId)),
+        Value(m_context, String::createExpectingAscii(m_context, moduleId)),
+        Value(m_context, String::createExpectingAscii(m_context, methodId)),
         Value::fromDynamic(m_context, std::move(arguments))
       });
     } catch (...) {
@@ -508,8 +510,8 @@ Value JSCExecutor::callFunctionSyncWithValue(
   SystraceSection s("JSCExecutor::callFunction");
 
   Object result = m_callFunctionReturnResultAndFlushedQueueJS->callAsFunction({
-    Value(m_context, String::createExpectingAscii(module)),
-    Value(m_context, String::createExpectingAscii(method)),
+    Value(m_context, String::createExpectingAscii(m_context, module)),
+    Value(m_context, String::createExpectingAscii(m_context, method)),
     std::move(args),
   }).asObject();
 
@@ -528,7 +530,7 @@ void JSCExecutor::setGlobalVariable(std::string propName, std::unique_ptr<const
     SystraceSection s("JSCExecutor.setGlobalVariable",
                       "propName", propName);
 
-    auto valueToInject = Value::fromJSON(m_context, jsStringFromBigString(*jsonValue));
+    auto valueToInject = Value::fromJSON(m_context, jsStringFromBigString(m_context, *jsonValue));
     Object::getGlobalObject(m_context).setProperty(propName.c_str(), valueToInject);
   } catch (...) {
     std::throw_with_nested(std::runtime_error("Error setting global variable: " + propName));
@@ -549,21 +551,19 @@ bool JSCExecutor::supportsProfiling() {
 
 void JSCExecutor::startProfiler(const std::string &titleString) {
   #ifdef WITH_JSC_EXTRA_TRACING
-  JSStringRef title = JSStringCreateWithUTF8CString(titleString.c_str());
+  String title(m_context, titleString.c_str());
   #if WITH_REACT_INTERNAL_SETTINGS
   JSStartProfiling(m_context, title, false);
   #else
   JSStartProfiling(m_context, title);
   #endif
-  JSStringRelease(title);
   #endif
 }
 
 void JSCExecutor::stopProfiler(const std::string &titleString, const std::string& filename) {
   #ifdef WITH_JSC_EXTRA_TRACING
-  JSStringRef title = JSStringCreateWithUTF8CString(titleString.c_str());
+  String title(m_context, titleString.c_str());
   facebook::react::stopAndOutputProfilingFile(m_context, title, filename.c_str());
-  JSStringRelease(title);
   #endif
 }
 
@@ -592,8 +592,8 @@ void JSCExecutor::flushQueueImmediate(Value&& queue) {
 
 void JSCExecutor::loadModule(uint32_t moduleId) {
   auto module = m_unbundle->getModule(moduleId);
-  auto sourceUrl = String::createExpectingAscii(module.name);
-  auto source = String::createExpectingAscii(module.code);
+  auto sourceUrl = String::createExpectingAscii(m_context, module.name);
+  auto source = String::createExpectingAscii(m_context, module.code);
   evaluateScript(m_context, source, sourceUrl);
 }
 
@@ -700,7 +700,7 @@ void JSCExecutor::terminateOwnedWebWorker(int workerId) {
 }
 
 Object JSCExecutor::createMessageObject(const std::string& msgJson) {
-  Value rebornJSMsg = Value::fromJSON(m_context, String(msgJson.c_str()));
+  Value rebornJSMsg = Value::fromJSON(m_context, String(m_context, msgJson.c_str()));
   Object messageObject = Object::create(m_context);
   messageObject.setProperty("data", rebornJSMsg);
   return messageObject;
@@ -714,7 +714,7 @@ void JSCExecutor::installNativeHook(const char* name) {
 
 JSValueRef JSCExecutor::getNativeModule(JSObjectRef object, JSStringRef propertyName) {
   if (JSStringIsEqualToUTF8CString(propertyName, "name")) {
-    return Value(m_context, String("NativeModules"));
+    return Value(m_context, String(m_context, "NativeModules"));
   }
 
   return m_nativeModules.getModule(m_context, propertyName);
diff --git a/ReactCommon/cxxreact/JSCLegacyProfiler.cpp b/ReactCommon/cxxreact/JSCLegacyProfiler.cpp
index 41a376b2d..2c811127b 100644
--- a/ReactCommon/cxxreact/JSCLegacyProfiler.cpp
+++ b/ReactCommon/cxxreact/JSCLegacyProfiler.cpp
@@ -29,13 +29,12 @@ static JSValueRef nativeProfilerStart(
     return Value::makeUndefined(ctx);
   }
 
-  JSStringRef title = JSValueToStringCopy(ctx, arguments[0], exception);
+  auto title = String::adopt(ctx, JSValueToStringCopy(ctx, arguments[0], exception));
   #if WITH_REACT_INTERNAL_SETTINGS
   JSStartProfiling(ctx, title, false);
   #else
   JSStartProfiling(ctx, title);
   #endif
-  JSStringRelease(title);
   return Value::makeUndefined(ctx);
 }
 
@@ -57,15 +56,15 @@ static JSValueRef nativeProfilerEnd(
 
   std::string writeLocation("/sdcard/");
   if (argumentCount > 1) {
-    JSStringRef fileName = JSValueToStringCopy(ctx, arguments[1], exception);
-    writeLocation += facebook::react::String::ref(fileName).str();
-    JSStringRelease(fileName);
+    auto fileName = String::adopt(
+      ctx, JSValueToStringCopy(ctx, arguments[1], exception));
+    writeLocation += fileName.str();
   } else {
     writeLocation += "profile.json";
   }
-  JSStringRef title = JSValueToStringCopy(ctx, arguments[0], exception);
+  auto title = String::adopt(
+    ctx, JSValueToStringCopy(ctx, arguments[0], exception));
   JSEndProfilingAndRender(ctx, title, writeLocation.c_str());
-  JSStringRelease(title);
   return Value::makeUndefined(ctx);
 }
 
diff --git a/ReactCommon/cxxreact/JSCLegacyTracing.cpp b/ReactCommon/cxxreact/JSCLegacyTracing.cpp
index 07419999a..7e684e510 100644
--- a/ReactCommon/cxxreact/JSCLegacyTracing.cpp
+++ b/ReactCommon/cxxreact/JSCLegacyTracing.cpp
@@ -32,13 +32,12 @@ static JSValueRef nativeTraceBeginLegacy(
     }
   }
 
-  JSStringRef title = JSStringCreateWithUTF8CString(ENABLED_FBSYSTRACE_PROFILE_NAME);
+  String title(ctx, ENABLED_FBSYSTRACE_PROFILE_NAME);
   #if WITH_REACT_INTERNAL_SETTINGS
   JSStartProfiling(ctx, title, true);
   #else
   JSStartProfiling(ctx, title);
   #endif
-  JSStringRelease(title);
 
   return Value::makeUndefined(ctx);
 }
@@ -57,9 +56,8 @@ static JSValueRef nativeTraceEndLegacy(
     }
   }
 
-  JSStringRef title = JSStringCreateWithUTF8CString(ENABLED_FBSYSTRACE_PROFILE_NAME);
+  String title(ctx, ENABLED_FBSYSTRACE_PROFILE_NAME);
   JSEndProfiling(ctx, title);
-  JSStringRelease(title);
 
   return Value::makeUndefined(ctx);
 }
diff --git a/ReactCommon/cxxreact/JSCMemory.cpp b/ReactCommon/cxxreact/JSCMemory.cpp
index ec8799d98..b639eae63 100644
--- a/ReactCommon/cxxreact/JSCMemory.cpp
+++ b/ReactCommon/cxxreact/JSCMemory.cpp
@@ -28,10 +28,9 @@ static JSValueRef nativeCaptureHeap(
       return Value::makeUndefined(ctx);
   }
 
-  JSStringRef outputFilename = JSValueToStringCopy(ctx, arguments[0], exception);
-  std::string finalFilename = facebook::react::String::ref(outputFilename).str();
-  JSCaptureHeap(ctx, finalFilename.c_str(), exception);
-  JSStringRelease(outputFilename);
+  auto outputFilename = String::adopt(
+    ctx, JSValueToStringCopy(ctx, arguments[0], exception));
+  JSCaptureHeap(ctx, outputFilename.str().c_str(), exception);
   return Value::makeUndefined(ctx);
 }
 
diff --git a/ReactCommon/cxxreact/JSCNativeModules.cpp b/ReactCommon/cxxreact/JSCNativeModules.cpp
index 564a80a98..b1036ba37 100644
--- a/ReactCommon/cxxreact/JSCNativeModules.cpp
+++ b/ReactCommon/cxxreact/JSCNativeModules.cpp
@@ -11,7 +11,7 @@ JSCNativeModules::JSCNativeModules(std::shared_ptr<ModuleRegistry> moduleRegistr
   m_moduleRegistry(std::move(moduleRegistry)) {}
 
 JSValueRef JSCNativeModules::getModule(JSContextRef context, JSStringRef jsName) {
-  std::string moduleName = String::ref(jsName).str();
+  std::string moduleName = String::ref(context, jsName).str();
 
   const auto it = m_objects.find(moduleName);
   if (it != m_objects.end()) {
diff --git a/ReactCommon/cxxreact/JSCUtils.cpp b/ReactCommon/cxxreact/JSCUtils.cpp
index 214d8641b..6a3239bb3 100644
--- a/ReactCommon/cxxreact/JSCUtils.cpp
+++ b/ReactCommon/cxxreact/JSCUtils.cpp
@@ -5,11 +5,11 @@
 namespace facebook {
 namespace react {
 
-String jsStringFromBigString(const JSBigString& bigstr) {
+String jsStringFromBigString(JSContextRef ctx, const JSBigString& bigstr) {
   if (bigstr.isAscii()) {
-    return String::createExpectingAscii(bigstr.c_str(), bigstr.size());
+    return String::createExpectingAscii(ctx, bigstr.c_str(), bigstr.size());
   } else {
-    return String(bigstr.c_str());
+    return String(ctx, bigstr.c_str());
   }
 }
 
diff --git a/ReactCommon/cxxreact/JSCUtils.h b/ReactCommon/cxxreact/JSCUtils.h
index 20acc40dd..e85b5564f 100644
--- a/ReactCommon/cxxreact/JSCUtils.h
+++ b/ReactCommon/cxxreact/JSCUtils.h
@@ -9,7 +9,7 @@
 namespace facebook {
 namespace react {
 
-String jsStringFromBigString(const JSBigString& bigstr);
+String jsStringFromBigString(JSContextRef ctx, const JSBigString& bigstr);
 
 }
 }
diff --git a/ReactCommon/cxxreact/JSCWebWorker.cpp b/ReactCommon/cxxreact/JSCWebWorker.cpp
index 360cebb83..e8bfa55cd 100644
--- a/ReactCommon/cxxreact/JSCWebWorker.cpp
+++ b/ReactCommon/cxxreact/JSCWebWorker.cpp
@@ -92,7 +92,7 @@ void JSCWebWorker::initJSVMAndLoadScript() {
 
   // TODO(9604438): Protect against script does not exist
   std::unique_ptr<const JSBigString> script = WebWorkerUtil::loadScriptFromAssets(scriptName_);
-  evaluateScript(context_, jsStringFromBigString(*script), String(scriptName_.c_str()));
+  evaluateScript(context_, jsStringFromBigString(context_, *script), String(context_, scriptName_.c_str()));
 
   installGlobalFunction(context_, "postMessage", nativePostMessage);
 }
@@ -127,7 +127,7 @@ JSValueRef JSCWebWorker::nativePostMessage(
 
 /*static*/
 Object JSCWebWorker::createMessageObject(JSContextRef context, const std::string& msgJson) {
-  Value rebornJSMsg = Value::fromJSON(context, String(msgJson.c_str()));
+  Value rebornJSMsg = Value::fromJSON(context, String(context, msgJson.c_str()));
   Object messageObject = Object::create(context);
   messageObject.setProperty("data", rebornJSMsg);
   return messageObject;
diff --git a/ReactCommon/cxxreact/tests/value.cpp b/ReactCommon/cxxreact/tests/value.cpp
index 8eac6d9bd..be2ee7bf6 100644
--- a/ReactCommon/cxxreact/tests/value.cpp
+++ b/ReactCommon/cxxreact/tests/value.cpp
@@ -12,7 +12,6 @@
 
 #include <stdexcept>
 
-using namespace facebook;
 using namespace facebook::react;
 
 #ifdef ANDROID
@@ -21,15 +20,14 @@ static void prepare() {
   ALooper_prepare(0);
 }
 #else
-static void prepare() {
-}
+static void prepare() {}
 #endif
 
 TEST(Value, Undefined) {
   prepare();
   JSGlobalContextRef ctx = JSGlobalContextCreateInGroup(nullptr, nullptr);
   auto v = Value::makeUndefined(ctx);
-  auto s = String::adopt(JSValueToStringCopy(ctx, v, nullptr));
+  auto s = String::adopt(ctx, JSValueToStringCopy(ctx, v, nullptr));
   EXPECT_EQ("undefined", s.str());
   JSGlobalContextRelease(ctx);
 }
@@ -37,7 +35,7 @@ TEST(Value, Undefined) {
 TEST(Value, FromJSON) {
   prepare();
   JSGlobalContextRef ctx = JSGlobalContextCreateInGroup(nullptr, nullptr);
-  react::String s("{\"a\": 4}");
+  String s(ctx, "{\"a\": 4}");
   Value v(Value::fromJSON(ctx, s));
   EXPECT_TRUE(JSValueIsObject(ctx, v));
   JSGlobalContextRelease(ctx);
@@ -46,7 +44,7 @@ TEST(Value, FromJSON) {
 TEST(Value, ToJSONString) {
   prepare();
   JSGlobalContextRef ctx = JSGlobalContextCreateInGroup(nullptr, nullptr);
-  react::String s("{\"a\": 4}");
+  String s(ctx, "{\"a\": 4}");
   Value v(Value::fromJSON(ctx, s));
   folly::dynamic dyn = folly::parseJson(v.toJSONString());
   ASSERT_NE(nullptr, dyn);
diff --git a/ReactCommon/jschelpers/JSCHelpers.cpp b/ReactCommon/jschelpers/JSCHelpers.cpp
index edf298f21..1b2d9f6c4 100644
--- a/ReactCommon/jschelpers/JSCHelpers.cpp
+++ b/ReactCommon/jschelpers/JSCHelpers.cpp
@@ -55,14 +55,14 @@ JSObjectRef makeFunction(
     JSContextRef ctx,
     const char* name,
     JSFunction function) {
-  return makeFunction(ctx, String(name), std::move(function));
+  return makeFunction(ctx, String(ctx, name), std::move(function));
 }
 
 void installGlobalFunction(
     JSGlobalContextRef ctx,
     const char* name,
     JSFunction function) {
-  auto jsName = String(name);
+  auto jsName = String(ctx, name);
   auto functionObj = makeFunction(ctx, jsName, std::move(function));
   Object::getGlobalObject(ctx).setProperty(jsName, Value(ctx, functionObj));
 }
@@ -71,7 +71,7 @@ JSObjectRef makeFunction(
     JSGlobalContextRef ctx,
     const char* name,
     JSObjectCallAsFunctionCallback callback) {
-  auto jsName = String(name);
+  auto jsName = String(ctx, name);
   return JSObjectMakeFunctionWithCallback(ctx, jsName, callback);
 }
 
@@ -79,9 +79,9 @@ void installGlobalFunction(
     JSGlobalContextRef ctx,
     const char* name,
     JSObjectCallAsFunctionCallback callback) {
-  String jsName(name);
+  String jsName(ctx, name);
   JSObjectRef functionObj = JSObjectMakeFunctionWithCallback(
-      ctx, jsName, callback);
+    ctx, jsName, callback);
   Object::getGlobalObject(ctx).setProperty(jsName, Value(ctx, functionObj));
 }
 
@@ -134,7 +134,7 @@ void formatAndThrowJSException(JSContextRef context, JSValueRef exn, JSStringRef
   // The null/empty-ness of source tells us if the JS came from a
   // file/resource, or was a constructed statement.  The location
   // info will include that source, if any.
-  std::string locationInfo = source != nullptr ? String::ref(source).str() : "";
+  std::string locationInfo = source != nullptr ? String::ref(context, source).str() : "";
   Object exObject = exception.asObject();
   auto line = exObject.getProperty("line");
   if (line != nullptr && line.isNumber()) {
diff --git a/ReactCommon/jschelpers/Value.cpp b/ReactCommon/jschelpers/Value.cpp
index 73f2ce69f..2bb0b61f2 100644
--- a/ReactCommon/jschelpers/Value.cpp
+++ b/ReactCommon/jschelpers/Value.cpp
@@ -46,7 +46,7 @@ std::string Value::toJSONString(unsigned indent) const {
     std::string exceptionText = Value(m_context, exn).toString().str();
     throwJSExecutionException("Exception creating JSON string: %s", exceptionText.c_str());
   }
-  return String::adopt(stringToAdopt).str();
+  return String::adopt(m_context, stringToAdopt).str();
 }
 
 /* static */
@@ -77,7 +77,7 @@ JSValueRef Value::fromDynamic(JSContextRef ctx, const folly::dynamic& value) {
   return jsVal;
 #else
   auto json = folly::toJson(value);
-  return fromJSON(ctx, String(json.c_str()));
+  return fromJSON(ctx, String(ctx, json.c_str()));
 #endif
 }
 
@@ -97,7 +97,7 @@ JSValueRef Value::fromDynamicInner(JSContextRef ctx, const folly::dynamic& obj)
       return JSValueMakeNumber(ctx, obj.asDouble());
 
     case folly::dynamic::Type::STRING:
-      return JSValueMakeString(ctx, String(obj.getString().c_str()));
+      return JSValueMakeString(ctx, String(ctx, obj.getString().c_str()));
 
     case folly::dynamic::Type::ARRAY: {
       // Collect JSValue for every element in the array
@@ -118,7 +118,7 @@ JSValueRef Value::fromDynamicInner(JSContextRef ctx, const folly::dynamic& obj)
         JSObjectSetProperty(
           ctx,
           jsObj,
-          String(it->first.asString().c_str()),
+          String(ctx, it->first.asString().c_str()),
           fromDynamicInner(ctx, it->second),
           kJSPropertyAttributeNone,
           nullptr);
@@ -147,7 +147,7 @@ Object Value::asObject() {
 Value Value::makeError(JSContextRef ctx, const char *error)
 {
   JSValueRef exn;
-  JSValueRef args[] = { Value(ctx, String(error)) };
+  JSValueRef args[] = { Value(ctx, String(ctx, error)) };
   JSObjectRef errorObj = JSObjectMakeError(ctx, 1, args, &exn);
   if (!errorObj) {
     std::string exceptionText = Value(ctx, exn).toString().str();
@@ -217,7 +217,7 @@ Value Object::getPropertyAtIndex(unsigned index) const {
 }
 
 Value Object::getProperty(const char *propName) const {
-  return getProperty(String(propName));
+  return getProperty(String(m_context, propName));
 }
 
 void Object::setProperty(const String& propName, const Value& value) const {
@@ -230,7 +230,7 @@ void Object::setProperty(const String& propName, const Value& value) const {
 }
 
 void Object::setProperty(const char *propName, const Value& value) const {
-  setProperty(String(propName), value);
+  setProperty(String(m_context, propName), value);
 }
 
 std::vector<String> Object::getPropertyNames() const {
@@ -239,7 +239,8 @@ std::vector<String> Object::getPropertyNames() const {
   std::vector<String> names;
   names.reserve(count);
   for (size_t i = 0; i < count; i++) {
-    names.emplace_back(String::ref(JSPropertyNameArrayGetNameAtIndex(namesRef, i)));
+    names.emplace_back(
+      String::ref(m_context, JSPropertyNameArrayGetNameAtIndex(namesRef, i)));
   }
   JSPropertyNameArrayRelease(namesRef);
   return names;
@@ -250,7 +251,8 @@ std::unordered_map<std::string, std::string> Object::toJSONMap() const {
   auto namesRef = JSObjectCopyPropertyNames(m_context, m_obj);
   size_t count = JSPropertyNameArrayGetCount(namesRef);
   for (size_t i = 0; i < count; i++) {
-    auto key = String::ref(JSPropertyNameArrayGetNameAtIndex(namesRef, i));
+    auto key = String::ref(m_context, 
+      JSPropertyNameArrayGetNameAtIndex(namesRef, i));
     map.emplace(key.str(), getProperty(key).toJSONString());
   }
   JSPropertyNameArrayRelease(namesRef);
diff --git a/ReactCommon/jschelpers/Value.h b/ReactCommon/jschelpers/Value.h
index 31b9736ce..ff96cfd06 100644
--- a/ReactCommon/jschelpers/Value.h
+++ b/ReactCommon/jschelpers/Value.h
@@ -47,18 +47,18 @@ private:
 
 class String : public noncopyable {
 public:
-  explicit String(const char* utf8) :
-    m_string(JSStringCreateWithUTF8CString(utf8))
+  explicit String(JSContextRef context, const char* utf8) :
+    m_context(context), m_string(JSStringCreateWithUTF8CString(utf8))
   {}
 
   String(String&& other) :
-    m_string(other.m_string)
+    m_context(other.m_context), m_string(other.m_string)
   {
     other.m_string = nullptr;
   }
 
   String(const String& other) :
-    m_string(other.m_string)
+    m_context(other.m_context), m_string(other.m_string)
   {
     if (m_string) {
       JSStringRetain(m_string);
@@ -111,35 +111,36 @@ public:
   }
 
   // This assumes ascii is nul-terminated.
-  static String createExpectingAscii(const char* ascii, size_t len) {
+  static String createExpectingAscii(JSContextRef context, const char* ascii, size_t len) {
 #if WITH_FBJSCEXTENSIONS
-    return String(JSStringCreateWithUTF8CStringExpectAscii(ascii, len), true);
+    return String(context, JSStringCreateWithUTF8CStringExpectAscii(ascii, len), true);
 #else
-    return String(JSStringCreateWithUTF8CString(ascii), true);
+    return String(context, JSStringCreateWithUTF8CString(ascii), true);
 #endif
   }
 
-  static String createExpectingAscii(std::string const &ascii) {
-    return createExpectingAscii(ascii.c_str(), ascii.size());
+  static String createExpectingAscii(JSContextRef context, std::string const &ascii) {
+    return createExpectingAscii(context, ascii.c_str(), ascii.size());
   }
 
-  static String ref(JSStringRef string) {
-    return String(string, false);
+  static String ref(JSContextRef context, JSStringRef string) {
+    return String(context, string, false);
   }
 
-  static String adopt(JSStringRef string) {
-    return String(string, true);
+  static String adopt(JSContextRef context, JSStringRef string) {
+    return String(context, string, true);
   }
 
 private:
-  explicit String(JSStringRef string, bool adopt) :
-    m_string(string)
+  explicit String(JSContextRef context, JSStringRef string, bool adopt) :
+    m_context(context), m_string(string)
   {
     if (!adopt && string) {
       JSStringRetain(string);
     }
   }
 
+  JSContextRef m_context;
   JSStringRef m_string;
 };
 
@@ -295,7 +296,7 @@ public:
   }
 
   String toString() noexcept {
-    return String::adopt(JSValueToStringCopy(context(), m_value, nullptr));
+    return String::adopt(context(), JSValueToStringCopy(context(), m_value, nullptr));
   }
 
   static Value makeError(JSContextRef ctx, const char *error);