diff --git a/benchmark/napi/function_args/binding.cc b/benchmark/napi/function_args/binding.cc
index 2c8fc7231f8..d0c1a079210 100644
--- a/benchmark/napi/function_args/binding.cc
+++ b/benchmark/napi/function_args/binding.cc
@@ -19,7 +19,7 @@ void CallWithString(const FunctionCallbackInfo<Value>& args) {
   assert(args.Length() == 1 && args[0]->IsString());
   if (args.Length() == 1 && args[0]->IsString()) {
     Local<String> str = args[0].As<String>();
-    const int32_t length = str->Utf8Length() + 1;
+    const int32_t length = str->Utf8Length(args.GetIsolate()) + 1;
     char* buf = new char[length];
     str->WriteUtf8(args.GetIsolate(), buf, length);
     delete [] buf;
diff --git a/src/node_api.cc b/src/node_api.cc
index 8ccadab3061..727ca0cf702 100644
--- a/src/node_api.cc
+++ b/src/node_api.cc
@@ -2399,7 +2399,7 @@ napi_status napi_get_value_string_utf8(napi_env env,
 
   if (!buf) {
     CHECK_ARG(env, result);
-    *result = val.As<v8::String>()->Utf8Length();
+    *result = val.As<v8::String>()->Utf8Length(env->isolate);
   } else {
     int copied = val.As<v8::String>()->WriteUtf8(
         env->isolate,
diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index 95ffaa1993f..9a280f7c127 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -599,7 +599,7 @@ void Fill(const FunctionCallbackInfo<Value>& args) {
   // Can't use StringBytes::Write() in all cases. For example if attempting
   // to write a two byte character into a one byte Buffer.
   if (enc == UTF8) {
-    str_length = str_obj->Utf8Length();
+    str_length = str_obj->Utf8Length(env->isolate());
     node::Utf8Value str(env->isolate(), args[1]);
     memcpy(ts_obj_data + start, *str, MIN(str_length, fill_length));
 
@@ -689,10 +689,11 @@ void StringWrite(const FunctionCallbackInfo<Value>& args) {
 }
 
 void ByteLengthUtf8(const FunctionCallbackInfo<Value> &args) {
+  Environment* env = Environment::GetCurrent(args);
   CHECK(args[0]->IsString());
 
   // Fast case: avoid StringBytes on UTF8 string. Jump to v8.
-  args.GetReturnValue().Set(args[0].As<String>()->Utf8Length());
+  args.GetReturnValue().Set(args[0].As<String>()->Utf8Length(env->isolate()));
 }
 
 // Normalize val to be an integer in the range of [1, -1] since
@@ -1062,7 +1063,7 @@ static void EncodeUtf8String(const FunctionCallbackInfo<Value>& args) {
   CHECK(args[0]->IsString());
 
   Local<String> str = args[0].As<String>();
-  size_t length = str->Utf8Length();
+  size_t length = str->Utf8Length(isolate);
   char* data = node::UncheckedMalloc(length);
   str->WriteUtf8(isolate,
                  data,
diff --git a/src/string_bytes.cc b/src/string_bytes.cc
index c106571a468..b7f009fe1fc 100644
--- a/src/string_bytes.cc
+++ b/src/string_bytes.cc
@@ -465,7 +465,7 @@ size_t StringBytes::Size(Isolate* isolate,
 
     case BUFFER:
     case UTF8:
-      return str->Utf8Length();
+      return str->Utf8Length(isolate);
 
     case UCS2:
       return str->Length() * sizeof(uint16_t);