diff --git a/nvflare/fuel/f3/cellnet/core_cell.py b/nvflare/fuel/f3/cellnet/core_cell.py
index 2e4f9695a1..57aeb7a9eb 100644
--- a/nvflare/fuel/f3/cellnet/core_cell.py
+++ b/nvflare/fuel/f3/cellnet/core_cell.py
@@ -943,7 +943,7 @@ def encrypt_payload(self, message: Message):
         payload_len = len(message.payload)
         message.add_headers(
             {
-                MessageHeaderKey.PAYLOAD_LEN: payload_len,
+                MessageHeaderKey.CLEAR_PAYLOAD_LEN: payload_len,
                 MessageHeaderKey.ENCRYPTED: True,
             }
         )
@@ -968,7 +968,7 @@ def decrypt_payload(self, message: Message):
         if not origin:
             raise RuntimeError("Message origin missing")
 
-        payload_len = message.get_header(MessageHeaderKey.PAYLOAD_LEN)
+        payload_len = message.get_header(MessageHeaderKey.CLEAR_PAYLOAD_LEN)
         origin_cert = self.cert_ex.get_certificate(origin)
         message.payload = self.credential_manager.decrypt(origin_cert, message.payload)
         if len(message.payload) != payload_len:
diff --git a/nvflare/fuel/f3/cellnet/defs.py b/nvflare/fuel/f3/cellnet/defs.py
index a481a8c0c4..de86aeed3e 100644
--- a/nvflare/fuel/f3/cellnet/defs.py
+++ b/nvflare/fuel/f3/cellnet/defs.py
@@ -42,6 +42,7 @@ class MessageHeaderKey:
     RETURN_REASON = CELLNET_PREFIX + "return_reason"
     SECURE = CELLNET_PREFIX + "secure"
     PAYLOAD_LEN = CELLNET_PREFIX + "payload_len"
+    CLEAR_PAYLOAD_LEN = CELLNET_PREFIX + "clear_payload_len"
     ENCRYPTED = CELLNET_PREFIX + "encrypted"
     OPTIONAL = CELLNET_PREFIX + "optional"