diff --git a/core/registry.js b/core/registry.js
index dc74003c4..3076bfef6 100644
--- a/core/registry.js
+++ b/core/registry.js
@@ -40,7 +40,7 @@ const Theme = goog.requireType('Blockly.Theme');
 /* eslint-disable-next-line no-unused-vars */
 const ToolboxItem = goog.requireType('Blockly.ToolboxItem');
 /* eslint-disable-next-line no-unused-vars */
-const ISerializer = goog.requireType('Blockly.serialization.ISerializer');
+const {ISerializer} = goog.requireType('Blockly.serialization.ISerializer');
 /* eslint-disable-next-line no-unused-vars */
 const {Cursor} = goog.requireType('Blockly.Cursor');
 
diff --git a/externs/goog-externs.js b/externs/goog-externs.js
index 8b956d4b0..dcc80965a 100644
--- a/externs/goog-externs.js
+++ b/externs/goog-externs.js
@@ -5,7 +5,17 @@
  */
 
 /**
- * @fileoverview Externs for goog.
+ * @fileoverview Externs for goog.*
+ *
+ * These are needed because we use goog.module, goog.require etc. to
+ * define our modules, but we don't actually include
+ * closure/goog/base.js as input to the compiler.  Originally we only
+ * needed the extern for goog, but some time between Closure Compiler
+ * versions 20210601.0.0 and 20211006.0.0 we started getting
+ * JSC_POSSIBLE_INEXISTENT_PROPERTY errors for goog.module /
+ * goog.require / goog.requireType declarations involving modules
+ * which used goog.module.declareLegacyNamespace.
+ *
  * @externs
  */
 
@@ -13,3 +23,44 @@
  * @type {!Object}
  */
 var goog = {};
+
+/**
+ * @param {string} name
+ * @return {void}
+ */
+goog.module = function(name) {};
+
+/**
+ * @return{void}
+ */
+goog.module.declareLegacyNamespace = function() {};
+
+/**
+ * @param {string} name
+ * @return {?}
+ */
+goog.module.get = function(name) {};
+
+/**
+ * @param {string} name
+ * @return {void}
+ */
+goog.provide = function(name) {};
+
+/**
+ * @param {string} namespace
+ * @return {?}
+ */
+goog.require = function(namespace) {};
+
+/**
+ * @param {string} namespace
+ * @return {?}
+ */
+goog.requireType = function(namespace) {};
+
+/**
+ * @param {string=} opt_message
+ * @return{void}
+ */
+goog.setTestOnly = function(opt_message) {};
diff --git a/package-lock.json b/package-lock.json
index b38f6a595..e962a4950 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -21,7 +21,7 @@
         "clang-format": "^1.5.0",
         "concurrently": "^6.0.0",
         "eslint": "^7.28.0",
-        "google-closure-compiler": "^20210601.0.0",
+        "google-closure-compiler": "^20211006.0.0",
         "google-closure-deps": "^20210601.0.0",
         "gulp": "^4.0.2",
         "gulp-concat": "^2.6.1",
@@ -6137,13 +6137,13 @@
       }
     },
     "node_modules/google-closure-compiler": {
-      "version": "20210601.0.0",
-      "resolved": "https://registry.npmjs.org/google-closure-compiler/-/google-closure-compiler-20210601.0.0.tgz",
-      "integrity": "sha512-lzzEoG2VTB7uUjnWnMyeZMU163w69HJpM27yh8Up9Ha5McHZeESjt3NRwU8cWMbCRdY06nFbRCDIVCRcadHCiw==",
+      "version": "20211006.0.0",
+      "resolved": "https://registry.npmjs.org/google-closure-compiler/-/google-closure-compiler-20211006.0.0.tgz",
+      "integrity": "sha512-WrzPLGtNMtgPubcvSur8JzzpuNn4feS7OMF74Hsm00G0qpdNvBVCIkMpnLr9SPZnl2vZ8UVqt83XVXMpQRTkUw==",
       "dev": true,
       "dependencies": {
         "chalk": "2.x",
-        "google-closure-compiler-java": "^20210601.0.0",
+        "google-closure-compiler-java": "^20211006.0.0",
         "minimist": "1.x",
         "vinyl": "2.x",
         "vinyl-sourcemaps-apply": "^0.2.0"
@@ -6155,21 +6155,21 @@
         "node": ">=10"
       },
       "optionalDependencies": {
-        "google-closure-compiler-linux": "^20210601.0.0",
-        "google-closure-compiler-osx": "^20210601.0.0",
-        "google-closure-compiler-windows": "^20210601.0.0"
+        "google-closure-compiler-linux": "^20211006.0.0",
+        "google-closure-compiler-osx": "^20211006.0.0",
+        "google-closure-compiler-windows": "^20211006.0.0"
       }
     },
     "node_modules/google-closure-compiler-java": {
-      "version": "20210601.0.0",
-      "resolved": "https://registry.npmjs.org/google-closure-compiler-java/-/google-closure-compiler-java-20210601.0.0.tgz",
-      "integrity": "sha512-bH6nIwOmp4qDWvlbXx5/DE3XA2aDGQoCpmRYZJGONY1Sy6Xfbq0ioXRHH9eBDP9hxhCJ5Sd/K89A0NZ8Nz9RJA==",
+      "version": "20211006.0.0",
+      "resolved": "https://registry.npmjs.org/google-closure-compiler-java/-/google-closure-compiler-java-20211006.0.0.tgz",
+      "integrity": "sha512-ggvk48GuP5Y8TD1I9dcJTu50+BQ2AfroAAsTV7nnbKdEPCZ/XJmGqy5qrJk0ImdAvONUHZETc5DMHHgFI5WjMg==",
       "dev": true
     },
     "node_modules/google-closure-compiler-linux": {
-      "version": "20210601.0.0",
-      "resolved": "https://registry.npmjs.org/google-closure-compiler-linux/-/google-closure-compiler-linux-20210601.0.0.tgz",
-      "integrity": "sha512-rnEQt7zz/1P1SfPhJiHQpfCgMPrsVVyEgDs09h67xn6+LXa9L0RP+hrJDEHqSWwjDPz0BkfUUv6zkqZvp1h/lw==",
+      "version": "20211006.0.0",
+      "resolved": "https://registry.npmjs.org/google-closure-compiler-linux/-/google-closure-compiler-linux-20211006.0.0.tgz",
+      "integrity": "sha512-7FclqwRDHcx9zvoy1JCQB3DC84T0anyOsb5kNIZgIf/oaUCvq27ElJK1X7W6IenOcwYyvDDWeDb38YkWl15ANw==",
       "cpu": [
         "x64",
         "x86"
@@ -6181,9 +6181,9 @@
       ]
     },
     "node_modules/google-closure-compiler-osx": {
-      "version": "20210601.0.0",
-      "resolved": "https://registry.npmjs.org/google-closure-compiler-osx/-/google-closure-compiler-osx-20210601.0.0.tgz",
-      "integrity": "sha512-A5r4s/WthR2iLMM0mxsluw8EW2AcOomC5ri/H6FjzpMq0RVEnLTgaGYdXolUAfEzH/7XtJJT2+JkYk3HSLCtrg==",
+      "version": "20211006.0.0",
+      "resolved": "https://registry.npmjs.org/google-closure-compiler-osx/-/google-closure-compiler-osx-20211006.0.0.tgz",
+      "integrity": "sha512-b0FGLvYZuMbDoLcu5z1lw0nWigpT8G29acuh4Yz6zO4NFq1aCpyR1X+BPhC2KCxb2eaMWPx2xoxbsekhkU0VzQ==",
       "cpu": [
         "x64",
         "x86",
@@ -6196,9 +6196,9 @@
       ]
     },
     "node_modules/google-closure-compiler-windows": {
-      "version": "20210601.0.0",
-      "resolved": "https://registry.npmjs.org/google-closure-compiler-windows/-/google-closure-compiler-windows-20210601.0.0.tgz",
-      "integrity": "sha512-6r94bPShnB0XXh9+5/qXGDHJN2PQGhF9yJPcgBZj+FAZlQGzlYkT0pkyp+loZT3lG+YRbjD28Lgo7xMcY4xgkA==",
+      "version": "20211006.0.0",
+      "resolved": "https://registry.npmjs.org/google-closure-compiler-windows/-/google-closure-compiler-windows-20211006.0.0.tgz",
+      "integrity": "sha512-7P13hA42LWIm4o+speQC5Yhs3D+3q9nvuItOxLCzess1sPDeBKi5dQi3w+C2MBTDyVN0CTKL86iClyyOnrbuRQ==",
       "cpu": [
         "x64"
       ],
@@ -18337,45 +18337,45 @@
       }
     },
     "google-closure-compiler": {
-      "version": "20210601.0.0",
-      "resolved": "https://registry.npmjs.org/google-closure-compiler/-/google-closure-compiler-20210601.0.0.tgz",
-      "integrity": "sha512-lzzEoG2VTB7uUjnWnMyeZMU163w69HJpM27yh8Up9Ha5McHZeESjt3NRwU8cWMbCRdY06nFbRCDIVCRcadHCiw==",
+      "version": "20211006.0.0",
+      "resolved": "https://registry.npmjs.org/google-closure-compiler/-/google-closure-compiler-20211006.0.0.tgz",
+      "integrity": "sha512-WrzPLGtNMtgPubcvSur8JzzpuNn4feS7OMF74Hsm00G0qpdNvBVCIkMpnLr9SPZnl2vZ8UVqt83XVXMpQRTkUw==",
       "dev": true,
       "requires": {
         "chalk": "2.x",
-        "google-closure-compiler-java": "^20210601.0.0",
-        "google-closure-compiler-linux": "^20210601.0.0",
-        "google-closure-compiler-osx": "^20210601.0.0",
-        "google-closure-compiler-windows": "^20210601.0.0",
+        "google-closure-compiler-java": "^20211006.0.0",
+        "google-closure-compiler-linux": "^20211006.0.0",
+        "google-closure-compiler-osx": "^20211006.0.0",
+        "google-closure-compiler-windows": "^20211006.0.0",
         "minimist": "1.x",
         "vinyl": "2.x",
         "vinyl-sourcemaps-apply": "^0.2.0"
       }
     },
     "google-closure-compiler-java": {
-      "version": "20210601.0.0",
-      "resolved": "https://registry.npmjs.org/google-closure-compiler-java/-/google-closure-compiler-java-20210601.0.0.tgz",
-      "integrity": "sha512-bH6nIwOmp4qDWvlbXx5/DE3XA2aDGQoCpmRYZJGONY1Sy6Xfbq0ioXRHH9eBDP9hxhCJ5Sd/K89A0NZ8Nz9RJA==",
+      "version": "20211006.0.0",
+      "resolved": "https://registry.npmjs.org/google-closure-compiler-java/-/google-closure-compiler-java-20211006.0.0.tgz",
+      "integrity": "sha512-ggvk48GuP5Y8TD1I9dcJTu50+BQ2AfroAAsTV7nnbKdEPCZ/XJmGqy5qrJk0ImdAvONUHZETc5DMHHgFI5WjMg==",
       "dev": true
     },
     "google-closure-compiler-linux": {
-      "version": "20210601.0.0",
-      "resolved": "https://registry.npmjs.org/google-closure-compiler-linux/-/google-closure-compiler-linux-20210601.0.0.tgz",
-      "integrity": "sha512-rnEQt7zz/1P1SfPhJiHQpfCgMPrsVVyEgDs09h67xn6+LXa9L0RP+hrJDEHqSWwjDPz0BkfUUv6zkqZvp1h/lw==",
+      "version": "20211006.0.0",
+      "resolved": "https://registry.npmjs.org/google-closure-compiler-linux/-/google-closure-compiler-linux-20211006.0.0.tgz",
+      "integrity": "sha512-7FclqwRDHcx9zvoy1JCQB3DC84T0anyOsb5kNIZgIf/oaUCvq27ElJK1X7W6IenOcwYyvDDWeDb38YkWl15ANw==",
       "dev": true,
       "optional": true
     },
     "google-closure-compiler-osx": {
-      "version": "20210601.0.0",
-      "resolved": "https://registry.npmjs.org/google-closure-compiler-osx/-/google-closure-compiler-osx-20210601.0.0.tgz",
-      "integrity": "sha512-A5r4s/WthR2iLMM0mxsluw8EW2AcOomC5ri/H6FjzpMq0RVEnLTgaGYdXolUAfEzH/7XtJJT2+JkYk3HSLCtrg==",
+      "version": "20211006.0.0",
+      "resolved": "https://registry.npmjs.org/google-closure-compiler-osx/-/google-closure-compiler-osx-20211006.0.0.tgz",
+      "integrity": "sha512-b0FGLvYZuMbDoLcu5z1lw0nWigpT8G29acuh4Yz6zO4NFq1aCpyR1X+BPhC2KCxb2eaMWPx2xoxbsekhkU0VzQ==",
       "dev": true,
       "optional": true
     },
     "google-closure-compiler-windows": {
-      "version": "20210601.0.0",
-      "resolved": "https://registry.npmjs.org/google-closure-compiler-windows/-/google-closure-compiler-windows-20210601.0.0.tgz",
-      "integrity": "sha512-6r94bPShnB0XXh9+5/qXGDHJN2PQGhF9yJPcgBZj+FAZlQGzlYkT0pkyp+loZT3lG+YRbjD28Lgo7xMcY4xgkA==",
+      "version": "20211006.0.0",
+      "resolved": "https://registry.npmjs.org/google-closure-compiler-windows/-/google-closure-compiler-windows-20211006.0.0.tgz",
+      "integrity": "sha512-7P13hA42LWIm4o+speQC5Yhs3D+3q9nvuItOxLCzess1sPDeBKi5dQi3w+C2MBTDyVN0CTKL86iClyyOnrbuRQ==",
       "dev": true,
       "optional": true
     },
diff --git a/package.json b/package.json
index 4964db70b..8f31af7dd 100644
--- a/package.json
+++ b/package.json
@@ -75,7 +75,7 @@
     "clang-format": "^1.5.0",
     "concurrently": "^6.0.0",
     "eslint": "^7.28.0",
-    "google-closure-compiler": "^20210601.0.0",
+    "google-closure-compiler": "^20211006.0.0",
     "google-closure-deps": "^20210601.0.0",
     "gulp": "^4.0.2",
     "gulp-concat": "^2.6.1",
diff --git a/scripts/gulpfiles/build_tasks.js b/scripts/gulpfiles/build_tasks.js
index 7010db859..dfcd0af87 100644
--- a/scripts/gulpfiles/build_tasks.js
+++ b/scripts/gulpfiles/build_tasks.js
@@ -91,7 +91,6 @@ var JSCOMP_ERROR = [
   // 'strictPrimitiveOperators',
   'suspiciousCode',
   'typeInvalidation',
-  'undefinedNames',
   'undefinedVars',
   'underscore',
   'unknownDefines',