diff --git a/lib/transport.js b/lib/transport.js
index e2771e4..b01cd51 100644
--- a/lib/transport.js
+++ b/lib/transport.js
@@ -21,7 +21,7 @@ async function sleep(ms) {
 async function sendToModem(partner, msg, modem, parentXid, part) {
     const xid = parentXid || uniqid();
 
-    const [msgHead, msgTail] = messageSplitter(msg.trim(), 140);
+    const [msgHead, msgTail] = messageSplitter(msg.trim(), Number(config.max_length) || 140);
     if (!msgHead) {
         return;
     }