diff --git a/packages/vite/src/node/optimizer/scan.ts b/packages/vite/src/node/optimizer/scan.ts
index f17231c52823e9..0380dc86a79513 100644
--- a/packages/vite/src/node/optimizer/scan.ts
+++ b/packages/vite/src/node/optimizer/scan.ts
@@ -435,7 +435,7 @@ function esbuildScanPlugin(
         }
         const { loader } = config.optimizeDeps?.esbuildOptions ?? {}
         return {
-          loader: loader[`.${ext}`] || ext as Loader,
+          loader: (loader && loader[`.${ext}`]) || ext as Loader,
           contents
         }
       })