diff --git a/packages/vite/src/node/optimizer/index.ts b/packages/vite/src/node/optimizer/index.ts
index f40802acb39039..ad81f13ee64dc0 100644
--- a/packages/vite/src/node/optimizer/index.ts
+++ b/packages/vite/src/node/optimizer/index.ts
@@ -253,9 +253,10 @@ export async function optimizeDeps(
         `Unable to parse dependency: ${id}. Trying again with a JSX transform.`
       )
       const transformed = await transformWithEsbuild(entryContent, filePath, {
-        loader: esbuildOptions.loader
-          ? esbuildOptions.loader[path.extname(filePath)]
-          : 'jsx'
+        loader:
+          (esbuildOptions.loader &&
+            esbuildOptions.loader[path.extname(filePath)]) ||
+          'jsx'
       })
       // Ensure that optimization won't fail by defaulting '.js' to the JSX parser.
       // This is useful for packages such as Gatsby.