diff --git a/binary/decoder_test.js b/binary/decoder_test.js
index b8e1084..7a71c0d 100644
--- a/binary/decoder_test.js
+++ b/binary/decoder_test.js
@@ -375,11 +375,11 @@ describe('binaryDecoderTest', () => {
 
     const decoder = jspb.BinaryDecoder.alloc(encoder.end());
 
-    expect(decoder.readString(ascii.length, true)).toEqual(ascii);
-    expect(utf8_two_bytes).toEqual(decoder.readString(2, true));
+    expect(decoder.readString(ascii.length,  /* enforceUtf8= */ true)).toEqual(ascii);
+    expect(utf8_two_bytes).toEqual(decoder.readString(2,  /* enforceUtf8= */ true));
     expect(utf8_three_bytes)
-      .toEqual(decoder.readString(3, true));
-    expect(utf8_four_bytes).toEqual(decoder.readString(4, true));
+      .toEqual(decoder.readString(3,  /* enforceUtf8= */ true));
+    expect(utf8_four_bytes).toEqual(decoder.readString(4,  /* enforceUtf8= */ true));
   });
 
   /**
diff --git a/generator/js_generator.cc b/generator/js_generator.cc
index 8136f58..6ca0ad3 100644
--- a/generator/js_generator.cc
+++ b/generator/js_generator.cc
@@ -1079,7 +1079,7 @@ std::string JSBinaryMethodType(const FieldDescriptor* field, bool is_writer) {
     name[0] = (name[0] - 'a') + 'A';
   }
   if (!is_writer && field->type() == FieldDescriptor::TYPE_STRING &&
-      field->file()->syntax() == FileDescriptor::SYNTAX_PROTO3) {
+      field->requires_utf8_validation()) {
     name = name + "RequireUtf8";
   }
   return IsIntegralFieldWithStringJSType(field) ? (name + "String") : name;