diff --git a/packages/@ngtools/webpack/src/extract_i18n_plugin.ts b/packages/@ngtools/webpack/src/extract_i18n_plugin.ts
index c3ce93e66946..a91422f46e03 100644
--- a/packages/@ngtools/webpack/src/extract_i18n_plugin.ts
+++ b/packages/@ngtools/webpack/src/extract_i18n_plugin.ts
@@ -175,7 +175,7 @@ export class ExtractI18nPlugin implements Tapable {
           program: this._program,
           host: this._compilerHost,
           angularCompilerOptions: this._angularCompilerOptions,
-          i18nFormat: this._i18nFormat,
+          i18nFormat: this._i18nFormat || '',
           locale: this._locale,
           outFile: this._outFile,