diff --git a/src/DIRAC/Core/DISET/private/Transports/BaseTransport.py b/src/DIRAC/Core/DISET/private/Transports/BaseTransport.py
index d3fb1e618eb..2e8558f7b99 100755
--- a/src/DIRAC/Core/DISET/private/Transports/BaseTransport.py
+++ b/src/DIRAC/Core/DISET/private/Transports/BaseTransport.py
@@ -176,6 +176,8 @@ def sendData(self, uData, prefix=b""):
                     sentBytes = result["Value"]
                 except Exception as e:
                     return S_ERROR(f"Exception while sending data: {e}")
+                if sentBytes < 0:
+                    return S_ERROR("Unknown unrecoverable error from socket while sending data")
                 if sentBytes == 0:
                     return S_ERROR("Connection closed by peer")
                 packSentBytes += sentBytes