diff --git a/packages/docusaurus/src/webpack/__tests__/utils.test.ts b/packages/docusaurus/src/webpack/__tests__/utils.test.ts
index 3b58b57d22..85a80f2ca5 100644
--- a/packages/docusaurus/src/webpack/__tests__/utils.test.ts
+++ b/packages/docusaurus/src/webpack/__tests__/utils.test.ts
@@ -74,7 +74,7 @@ describe('extending generated webpack config', () => {
           filename: 'new.bundle.js',
         };
       }
-      return {};
+      // Implicitly returning undefined to test null-safety
     };
 
     config = applyConfigureWebpack(configureWebpack, config, false, undefined, {
diff --git a/packages/docusaurus/src/webpack/utils.ts b/packages/docusaurus/src/webpack/utils.ts
index 14568c890d..f9626b8196 100644
--- a/packages/docusaurus/src/webpack/utils.ts
+++ b/packages/docusaurus/src/webpack/utils.ts
@@ -184,12 +184,8 @@ export function applyConfigureWebpack(
     getJSLoader: getCustomizableJSLoader(jsLoader),
   };
   if (typeof configureWebpack === 'function') {
-    const {mergeStrategy, ...res} = configureWebpack(
-      config,
-      isServer,
-      utils,
-      content,
-    );
+    const {mergeStrategy, ...res} =
+      configureWebpack(config, isServer, utils, content) ?? {};
     if (res && typeof res === 'object') {
       const customizeRules = mergeStrategy ?? {};
       return mergeWithCustomize({