diff --git a/modem/arq_session_iss.py b/modem/arq_session_iss.py
index a7250056..67cd6d1d 100644
--- a/modem/arq_session_iss.py
+++ b/modem/arq_session_iss.py
@@ -26,7 +26,7 @@ class ARQSessionISS(arq_session.ARQSession):
     # DJ2LS: 3.5 seconds is working well WITHOUT a channel busy detection delay
     TIMEOUT_CHANNEL_BUSY = 0
     TIMEOUT_CONNECT_ACK = 3.5 + TIMEOUT_CHANNEL_BUSY
-    TIMEOUT_TRANSFER = 1 + TIMEOUT_CHANNEL_BUSY
+    TIMEOUT_TRANSFER = 1.5 + TIMEOUT_CHANNEL_BUSY
     TIMEOUT_STOP_ACK = 3.5 + TIMEOUT_CHANNEL_BUSY
 
     STATE_TRANSITION = {