diff --git a/lib/cwmp.ts b/lib/cwmp.ts
index 4a1bf5d..fb94b56 100644
--- a/lib/cwmp.ts
+++ b/lib/cwmp.ts
@@ -1231,7 +1231,8 @@ async function listenerAsync(
   }
 
   if (!charset) {
-    const e = parseXmlDeclaration(body).find(s => s.localName === "encoding");
+    const parse = parseXmlDeclaration(body);
+    const e = parse ? parse.find(s => s.localName === "encoding") : null;
     charset = e ? e.value : "utf8";
   }