diff --git a/src/extension-support/extension-manager.js b/src/extension-support/extension-manager.js
index 5ffefa1b..341f2461 100644
--- a/src/extension-support/extension-manager.js
+++ b/src/extension-support/extension-manager.js
@@ -11,7 +11,7 @@ const BlockType = require('./block-type');
 const builtinExtensions = {
     // This is an example that isn't loaded with the other core blocks,
     // but serves as a reference for loading core blocks as extensions.
-    coreExample: require('../blocks/scratch3_core_example'),
+    coreExample: () => require('../blocks/scratch3_core_example'),
     // These are the non-core built-in extensions.
     pen: () => require('../extensions/scratch3_pen'),
     wedo2: () => require('../extensions/scratch3_wedo2'),
@@ -118,19 +118,22 @@ class ExtensionManager {
      * @param {string} extensionId - the ID of an internal extension
      */
     loadExtensionIdSync (extensionId) {
-        if (builtinExtensions.hasOwnProperty(extensionId)) {
-            /** @TODO dupe handling for non-builtin extensions. See commit 670e51d33580e8a2e852b3b038bb3afc282f81b9 */
-            if (this.isExtensionLoaded(extensionId)) {
-                const message = `Rejecting attempt to load a second extension with ID ${extensionId}`;
-                log.warn(message);
-                return;
-            }
-
-            const extension = builtinExtensions[extensionId];
-            const extensionInstance = new extension(this.runtime);
-            const serviceName = this._registerInternalExtension(extensionInstance);
-            this._loadedExtensions.set(extensionId, serviceName);
+        if (!builtinExtensions.hasOwnProperty(extensionId)) {
+            log.warn(`Could not find extension ${extensionId} in the built in extensions.`);
+            return;
         }
+
+        /** @TODO dupe handling for non-builtin extensions. See commit 670e51d33580e8a2e852b3b038bb3afc282f81b9 */
+        if (this.isExtensionLoaded(extensionId)) {
+            const message = `Rejecting attempt to load a second extension with ID ${extensionId}`;
+            log.warn(message);
+            return;
+        }
+
+        const extension = builtinExtensions[extensionId]();
+        const extensionInstance = new extension(this.runtime);
+        const serviceName = this._registerInternalExtension(extensionInstance);
+        this._loadedExtensions.set(extensionId, serviceName);
     }
 
     /**
diff --git a/test/unit/dispatch.js b/test/unit/dispatch.js
index f3b94407..dfd00155 100644
--- a/test/unit/dispatch.js
+++ b/test/unit/dispatch.js
@@ -75,11 +75,8 @@ test('local, sync', t => {
     const c = dispatch.callSync('SyncDispatchTest', 'doubleArgument', 123);
     t.equal(c, 246);
 
-    try {
-        dispatch.callSync('SyncDispatchTest', 'throwException');
-    } catch (e) {
-        t.equal(e.message, 'This is a test exception thrown by DispatchTest');
-    }
+    t.throws(() => dispatch.callSync('SyncDispatchTest', 'throwException'),
+        new Error('This is a test exception thrown by DispatchTest'));
 
     t.end();
 });