diff --git a/packages/vite/src/node/plugins/css.ts b/packages/vite/src/node/plugins/css.ts
index 85a8b6daaf037c..48d19b14873aee 100644
--- a/packages/vite/src/node/plugins/css.ts
+++ b/packages/vite/src/node/plugins/css.ts
@@ -246,7 +246,7 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
         return
       }
 
-      const modules = cssModulesCache.get(config)!.get(id)
+      const modules = cssModulesCache.get(config)?.get(id)
       const modulesCode =
         modules && dataToEsm(modules, { namedExports: true, preferConst: true })