diff --git a/js/flatbuffers.js b/js/flatbuffers.js
index f3c483425..6c3d15cc8 100644
--- a/js/flatbuffers.js
+++ b/js/flatbuffers.js
@@ -88,6 +88,16 @@ flatbuffers.Long = function(low, high) {
   this.high = high | 0;
 };
 
+/**
+ * @param {number} high
+ * @param {number} low
+ * @returns {flatbuffers.Long}
+ */
+flatbuffers.Long.create = function(low, high) {
+  // Special-case zero to avoid GC overhead for default values
+  return low == 0 && high == 0 ? flatbuffers.Long.ZERO : new flatbuffers.Long(low, high);
+};
+
 /**
  * @returns {number}
  */
@@ -751,6 +761,17 @@ flatbuffers.Builder.prototype.createString = function(s) {
   }
   return this.endVector();
 };
+
+/**
+ * A helper function to avoid generated code depending on this file directly.
+ *
+ * @param {number} low
+ * @param {number} high
+ * @returns {flatbuffers.Long}
+ */
+flatbuffers.Builder.prototype.createLong = function(low, high) {
+  return flatbuffers.Long.create(low, high);
+};
 ////////////////////////////////////////////////////////////////////////////////
 /// @cond FLATBUFFERS_INTERNAL
 /**
@@ -1101,6 +1122,17 @@ flatbuffers.ByteBuffer.prototype.__has_identifier = function(ident) {
   return true;
 };
 
+/**
+ * A helper function to avoid generated code depending on this file directly.
+ *
+ * @param {number} low
+ * @param {number} high
+ * @returns {flatbuffers.Long}
+ */
+flatbuffers.ByteBuffer.prototype.createLong = function(low, high) {
+  return flatbuffers.Long.create(low, high);
+};
+
 // Exports for Node.js and RequireJS
 this.flatbuffers = flatbuffers;
 
diff --git a/src/idl_gen_js.cpp b/src/idl_gen_js.cpp
index 7efc39571..f31d70f5a 100644
--- a/src/idl_gen_js.cpp
+++ b/src/idl_gen_js.cpp
@@ -189,7 +189,7 @@ static std::string GenGetter(const Type &type, const std::string &arguments) {
   }
 }
 
-static std::string GenDefaultValue(const Value &value) {
+static std::string GenDefaultValue(const Value &value, const std::string &context) {
   if (value.type.enum_def) {
     if (auto val = value.type.enum_def->ReverseLookup(
         atoi(value.constant.c_str()), false)) {
@@ -205,13 +205,11 @@ static std::string GenDefaultValue(const Value &value) {
       return "null";
 
     case BASE_TYPE_LONG:
-    case BASE_TYPE_ULONG:
-      if (value.constant != "0") {
-        int64_t constant = StringToInt(value.constant.c_str());
-        return "new flatbuffers.Long(" + NumToString((int32_t)constant) +
-          ", " + NumToString((int32_t)(constant >> 32)) + ")";
-      }
-      return "flatbuffers.Long.ZERO";
+    case BASE_TYPE_ULONG: {
+      int64_t constant = StringToInt(value.constant.c_str());
+      return context + ".createLong(" + NumToString((int32_t)constant) +
+        ", " + NumToString((int32_t)(constant >> 32)) + ")";
+    }
 
     default:
       return value.constant;
@@ -417,7 +415,7 @@ static void GenStruct(const Parser &parser, StructDef &struct_def,
           index += ", optionalEncoding";
         }
         code += offset_prefix + GenGetter(field.value.type,
-          "(" + index + ")") + " : " + GenDefaultValue(field.value);
+          "(" + index + ")") + " : " + GenDefaultValue(field.value, "this.bb");
         code += ";\n";
       }
     }
@@ -485,7 +483,7 @@ static void GenStruct(const Parser &parser, StructDef &struct_def,
             code += "false";
           } else if (field.value.type.element == BASE_TYPE_LONG ||
               field.value.type.element == BASE_TYPE_ULONG) {
-            code += "flatbuffers.Long.ZERO";
+            code += "this.bb.createLong(0, 0)";
           } else if (IsScalar(field.value.type.element)) {
             code += "0";
           } else {
@@ -570,7 +568,7 @@ static void GenStruct(const Parser &parser, StructDef &struct_def,
         if (field.value.type.base_type == BASE_TYPE_BOOL) {
           code += "+";
         }
-        code += GenDefaultValue(field.value);
+        code += GenDefaultValue(field.value, "builder");
       }
       code += ");\n};\n\n";
 
diff --git a/tests/JavaScriptTest.js b/tests/JavaScriptTest.js
index 8eb50f3c5..3ed8b5156 100644
--- a/tests/JavaScriptTest.js
+++ b/tests/JavaScriptTest.js
@@ -67,6 +67,7 @@ function main() {
   // Test it:
   testBuffer(fbb.dataBuffer());
 
+  test64bit();
   testUnicode();
   fuzzTest1();
 
@@ -117,6 +118,52 @@ function testBuffer(bb) {
   assert.strictEqual(monster.testbool(), false);
 }
 
+function test64bit() {
+  var fbb = new flatbuffers.Builder();
+  var required = fbb.createString('required');
+
+  MyGame.Example.Stat.startStat(fbb);
+  var stat2 = MyGame.Example.Stat.endStat(fbb);
+
+  MyGame.Example.Monster.startMonster(fbb);
+  MyGame.Example.Monster.addName(fbb, required);
+  MyGame.Example.Monster.addTestempty(fbb, stat2);
+  var mon2 = MyGame.Example.Monster.endMonster(fbb);
+
+  MyGame.Example.Stat.startStat(fbb);
+  MyGame.Example.Stat.addVal(fbb, new flatbuffers.Long(0x12345678, 0x23456789));
+  var stat = MyGame.Example.Stat.endStat(fbb);
+
+  MyGame.Example.Monster.startMonster(fbb);
+  MyGame.Example.Monster.addName(fbb, required);
+  MyGame.Example.Monster.addEnemy(fbb, mon2);
+  MyGame.Example.Monster.addTestempty(fbb, stat);
+  var mon = MyGame.Example.Monster.endMonster(fbb);
+
+  MyGame.Example.Monster.finishMonsterBuffer(fbb, mon);
+  var bytes = fbb.asUint8Array();
+
+  ////////////////////////////////////////////////////////////////
+
+  var bb = new flatbuffers.ByteBuffer(bytes);
+  assert.ok(MyGame.Example.Monster.bufferHasIdentifier(bb));
+  var mon = MyGame.Example.Monster.getRootAsMonster(bb);
+
+  var stat = mon.testempty();
+  assert.strictEqual(stat != null, true);
+  assert.strictEqual(stat.val() != null, true);
+  assert.strictEqual(stat.val().low, 0x12345678);
+  assert.strictEqual(stat.val().high, 0x23456789);
+
+  var mon2 = mon.enemy();
+  assert.strictEqual(mon2 != null, true);
+  stat = mon2.testempty();
+  assert.strictEqual(stat != null, true);
+  assert.strictEqual(stat.val() != null, true);
+  assert.strictEqual(stat.val().low, 0); // default value
+  assert.strictEqual(stat.val().high, 0);
+}
+
 function testUnicode() {
   var correct = fs.readFileSync('unicode_test.mon');
   var json = JSON.parse(fs.readFileSync('unicode_test.json', 'utf8'));
diff --git a/tests/monster_test_generated.js b/tests/monster_test_generated.js
index 9d0f48b09..77c41d7f1 100644
--- a/tests/monster_test_generated.js
+++ b/tests/monster_test_generated.js
@@ -300,7 +300,7 @@ MyGame.Example.Stat.prototype.id = function(optionalEncoding) {
  */
 MyGame.Example.Stat.prototype.val = function() {
   var offset = this.bb.__offset(this.bb_pos, 6);
-  return offset ? this.bb.readInt64(this.bb_pos + offset) : flatbuffers.Long.ZERO;
+  return offset ? this.bb.readInt64(this.bb_pos + offset) : this.bb.createLong(0, 0);
 };
 
 /**
@@ -331,7 +331,7 @@ MyGame.Example.Stat.addId = function(builder, idOffset) {
  * @param {flatbuffers.Long} val
  */
 MyGame.Example.Stat.addVal = function(builder, val) {
-  builder.addFieldInt64(1, val, flatbuffers.Long.ZERO);
+  builder.addFieldInt64(1, val, builder.createLong(0, 0));
 };
 
 /**
@@ -593,7 +593,7 @@ MyGame.Example.Monster.prototype.testhashu32Fnv1 = function() {
  */
 MyGame.Example.Monster.prototype.testhashs64Fnv1 = function() {
   var offset = this.bb.__offset(this.bb_pos, 40);
-  return offset ? this.bb.readInt64(this.bb_pos + offset) : flatbuffers.Long.ZERO;
+  return offset ? this.bb.readInt64(this.bb_pos + offset) : this.bb.createLong(0, 0);
 };
 
 /**
@@ -601,7 +601,7 @@ MyGame.Example.Monster.prototype.testhashs64Fnv1 = function() {
  */
 MyGame.Example.Monster.prototype.testhashu64Fnv1 = function() {
   var offset = this.bb.__offset(this.bb_pos, 42);
-  return offset ? this.bb.readUint64(this.bb_pos + offset) : flatbuffers.Long.ZERO;
+  return offset ? this.bb.readUint64(this.bb_pos + offset) : this.bb.createLong(0, 0);
 };
 
 /**
@@ -625,7 +625,7 @@ MyGame.Example.Monster.prototype.testhashu32Fnv1a = function() {
  */
 MyGame.Example.Monster.prototype.testhashs64Fnv1a = function() {
   var offset = this.bb.__offset(this.bb_pos, 48);
-  return offset ? this.bb.readInt64(this.bb_pos + offset) : flatbuffers.Long.ZERO;
+  return offset ? this.bb.readInt64(this.bb_pos + offset) : this.bb.createLong(0, 0);
 };
 
 /**
@@ -633,7 +633,7 @@ MyGame.Example.Monster.prototype.testhashs64Fnv1a = function() {
  */
 MyGame.Example.Monster.prototype.testhashu64Fnv1a = function() {
   var offset = this.bb.__offset(this.bb_pos, 50);
-  return offset ? this.bb.readUint64(this.bb_pos + offset) : flatbuffers.Long.ZERO;
+  return offset ? this.bb.readUint64(this.bb_pos + offset) : this.bb.createLong(0, 0);
 };
 
 /**
@@ -893,7 +893,7 @@ MyGame.Example.Monster.addTesthashu32Fnv1 = function(builder, testhashu32Fnv1) {
  * @param {flatbuffers.Long} testhashs64Fnv1
  */
 MyGame.Example.Monster.addTesthashs64Fnv1 = function(builder, testhashs64Fnv1) {
-  builder.addFieldInt64(18, testhashs64Fnv1, flatbuffers.Long.ZERO);
+  builder.addFieldInt64(18, testhashs64Fnv1, builder.createLong(0, 0));
 };
 
 /**
@@ -901,7 +901,7 @@ MyGame.Example.Monster.addTesthashs64Fnv1 = function(builder, testhashs64Fnv1) {
  * @param {flatbuffers.Long} testhashu64Fnv1
  */
 MyGame.Example.Monster.addTesthashu64Fnv1 = function(builder, testhashu64Fnv1) {
-  builder.addFieldInt64(19, testhashu64Fnv1, flatbuffers.Long.ZERO);
+  builder.addFieldInt64(19, testhashu64Fnv1, builder.createLong(0, 0));
 };
 
 /**
@@ -925,7 +925,7 @@ MyGame.Example.Monster.addTesthashu32Fnv1a = function(builder, testhashu32Fnv1a)
  * @param {flatbuffers.Long} testhashs64Fnv1a
  */
 MyGame.Example.Monster.addTesthashs64Fnv1a = function(builder, testhashs64Fnv1a) {
-  builder.addFieldInt64(22, testhashs64Fnv1a, flatbuffers.Long.ZERO);
+  builder.addFieldInt64(22, testhashs64Fnv1a, builder.createLong(0, 0));
 };
 
 /**
@@ -933,7 +933,7 @@ MyGame.Example.Monster.addTesthashs64Fnv1a = function(builder, testhashs64Fnv1a)
  * @param {flatbuffers.Long} testhashu64Fnv1a
  */
 MyGame.Example.Monster.addTesthashu64Fnv1a = function(builder, testhashu64Fnv1a) {
-  builder.addFieldInt64(23, testhashu64Fnv1a, flatbuffers.Long.ZERO);
+  builder.addFieldInt64(23, testhashu64Fnv1a, builder.createLong(0, 0));
 };
 
 /**