diff --git a/package/browser/core.js b/package/browser/core.js
index b385cb8ca..3dde18168 100644
--- a/package/browser/core.js
+++ b/package/browser/core.js
@@ -24,6 +24,9 @@
 'use strict';
 
 // Add a helper method to set the Blockly locale.
-Blockly.setLocale = function(locale) {
-  Blockly.Msg = Object.assign(Blockly.Msg || {}, locale);
-};
\ No newline at end of file
+Blockly.setLocale = function (locale) {
+  Blockly.Msg = Blockly.Msg || {};
+  Object.keys(locale).forEach(function (k) {
+    Blockly.Msg[k] = locale[k];
+  });
+};
diff --git a/package/browser/index.js b/package/browser/index.js
index 390d24fa7..32fac243c 100644
--- a/package/browser/index.js
+++ b/package/browser/index.js
@@ -27,6 +27,9 @@
 // Include the EN Locale by default.
 Blockly.setLocale(En);
 
-Blockly.Blocks = Object.assign(Blockly.Blocks, BlocklyBlocks);
+Blockly.Blocks = Blockly.Blocks || {};
+Object.keys(BlocklyBlocks).forEach(function (k) {
+  Blockly.Blocks[k] = BlocklyBlocks[k];
+});
 
 Blockly.JavaScript = BlocklyJS;
\ No newline at end of file
diff --git a/package/node/core.js b/package/node/core.js
index 951f8c85a..41d6ff60c 100644
--- a/package/node/core.js
+++ b/package/node/core.js
@@ -24,6 +24,9 @@
 'use strict';
 
 // Add a helper method to set the Blockly locale.
-Blockly.setLocale = function(locale) {
-  Blockly.Msg = Object.assign(Blockly.Msg || {}, locale);
-};
\ No newline at end of file
+Blockly.setLocale = function (locale) {
+  Blockly.Msg = Blockly.Msg || {};
+  Object.keys(locale).forEach(function (k) {
+    Blockly.Msg[k] = locale[k];
+  });
+};
diff --git a/package/node/index.js b/package/node/index.js
index 718a1ee48..003e5bfcd 100644
--- a/package/node/index.js
+++ b/package/node/index.js
@@ -26,7 +26,10 @@
 // Include the EN Locale by default.
 Blockly.setLocale(En);
 
-Blockly.Blocks = Object.assign(Blockly.Blocks, BlocklyBlocks);
+Blockly.Blocks = Blockly.Blocks || {};
+Object.keys(BlocklyBlocks).forEach(function (k) {
+  Blockly.Blocks[k] = BlocklyBlocks[k];
+});
 
 Blockly.JavaScript = BlocklyJS;