diff --git a/src/utils/cubismdebug.ts b/src/utils/cubismdebug.ts
index dff0cfb..6d6877f 100644
--- a/src/utils/cubismdebug.ts
+++ b/src/utils/cubismdebug.ts
@@ -8,7 +8,7 @@
 import { CubismFramework, LogLevel } from '../live2dcubismframework';
 
 export const CSM_ASSERT =
-  process.env.NODE_ENV === 'production'
+  (typeof process !== 'undefined' && process.env.NODE_ENV === 'production')
     ? () => {}
     : (expr: any) => console.assert(expr);