diff --git a/lib/internal/modules/esm/assert.js b/lib/internal/modules/esm/assert.js
index eed80313d463f2..2f11890b0e6af1 100644
--- a/lib/internal/modules/esm/assert.js
+++ b/lib/internal/modules/esm/assert.js
@@ -2,6 +2,7 @@
 
 const {
   ArrayPrototypeFilter,
+  ArrayPrototypeFlat,
   ArrayPrototypeIncludes,
   ObjectKeys,
   ObjectPrototypeHasOwnProperty,
@@ -39,7 +40,7 @@ const formatTypeMap = {
  * @type {Array<string, string>}
  */
 const supportedAssertionTypes = ArrayPrototypeFilter(
-  ObjectValues(formatTypeMap),
+  ArrayPrototypeFlat(ObjectValues(formatTypeMap)),
   (type) => type !== kImplicitAssertType);
 
 
diff --git a/test/es-module/test-import-jsonc.js b/test/es-module/test-import-jsonc.js
index 02db56c6b93b99..bd3a0c0c0b2786 100644
--- a/test/es-module/test-import-jsonc.js
+++ b/test/es-module/test-import-jsonc.js
@@ -1,6 +1,6 @@
 'use strict';
 
-const common = require('../common');
+require('../common');
 const assert = require('assert');
 
 const jsonFiles = [
@@ -19,4 +19,4 @@ for (const [file, [throwWithTypeJSON, throwWithTypeJSONC]] of jsonFiles) {
   assert[throwWithTypeJSONC ? 'rejects' : 'doesNotReject'](async () => {
     await import(file, { with: { type: 'jsonc' } });
   });
-}
\ No newline at end of file
+}