diff --git a/scripts/gulpfiles/build_tasks.js b/scripts/gulpfiles/build_tasks.js
index cd80b132efb..ed81e7cc115 100644
--- a/scripts/gulpfiles/build_tasks.js
+++ b/scripts/gulpfiles/build_tasks.js
@@ -677,7 +677,8 @@ function buildCompiled() {
 /**
  * This task builds the shims used by the playgrounds and tests to
  * load Blockly in either compressed or uncompressed mode, creating
- * build/blockly.mjs, blocks.mjs, javascript.mjs, etc.
+ * build/blockly.loader.mjs, blocks.loader.mjs, javascript.loader.mjs,
+ * etc.
  *
  * Prerequisite: getChunkOptions (via buildCompiled, for chunks[].parent).
  */
@@ -702,7 +703,7 @@ async function buildShims() {
     const modulePath = posixPath(chunk.moduleEntry ?? chunk.entry);
     const scriptPath =
         path.posix.join(RELEASE_DIR, `${chunk.name}${COMPILED_SUFFIX}.js`);
-    const shimPath = path.join(BUILD_DIR, `${chunk.name}.mjs`);
+    const shimPath = path.join(BUILD_DIR, `${chunk.name}.loader.mjs`);
     const parentImport =
         chunk.parent ? `import ${quote(`./${chunk.parent.name}.mjs`)};` : '';
     const exports = await import(`../../${modulePath}`);
diff --git a/tests/multi_playground.html b/tests/multi_playground.html
index e225be23a7f..f929de8d8b1 100644
--- a/tests/multi_playground.html
+++ b/tests/multi_playground.html
@@ -7,8 +7,8 @@
     <script type="module">
       import {COMPRESSED, loadScript} from './scripts/load.mjs';
 
-      import * as Blockly from '../build/blockly.mjs';
-      import '../build/blocks.mjs';
+      import * as Blockly from '../build/blockly.loader.mjs';
+      import '../build/blocks.loader.mjs';
 
       await loadScript('../build/msg/en.js');
 
diff --git a/tests/playground.html b/tests/playground.html
index f1c8512d900..9116a599e1c 100644
--- a/tests/playground.html
+++ b/tests/playground.html
@@ -7,13 +7,13 @@
     <script type="module">
       import {COMPRESSED, loadScript} from './scripts/load.mjs';
 
-      import * as Blockly from '../build/blockly.mjs';
-      import '../build/blocks.mjs';
-      import {dartGenerator} from '../build/dart.mjs';
-      import {luaGenerator} from '../build/lua.mjs';
-      import {javascriptGenerator} from '../build/javascript.mjs';
-      import {phpGenerator} from '../build/php.mjs';
-      import {pythonGenerator} from '../build/python.mjs';
+      import * as Blockly from '../build/blockly.loader.mjs';
+      import '../build/blocks.loader.mjs';
+      import {dartGenerator} from '../build/dart.loader.mjs';
+      import {luaGenerator} from '../build/lua.loader.mjs';
+      import {javascriptGenerator} from '../build/javascript.loader.mjs';
+      import {phpGenerator} from '../build/php.loader.mjs';
+      import {pythonGenerator} from '../build/python.loader.mjs';
 
       await loadScript('../build/msg/en.js');
       await loadScript('playgrounds/screenshot.js');
diff --git a/tests/playgrounds/advanced_playground.html b/tests/playgrounds/advanced_playground.html
index 4406dc4293d..515ff557f2a 100644
--- a/tests/playgrounds/advanced_playground.html
+++ b/tests/playgrounds/advanced_playground.html
@@ -7,8 +7,8 @@
     <script type="module">
       import {loadScript} from '../scripts/load.mjs';
 
-      import * as Blockly from '../../build/blockly.mjs';
-      import '../../build/blocks.mjs';
+      import * as Blockly from '../../build/blockly.loader.mjs';
+      import '../../build/blocks.loader.mjs';
       // Generators not needed (but see also bug #6597).
 
       await loadScript('../../build/msg/en.js');