Index: /trunk/src/VBox/Devices/Network/slirp/tftp.c
===================================================================
--- /trunk/src/VBox/Devices/Network/slirp/tftp.c	(revision 42189)
+++ /trunk/src/VBox/Devices/Network/slirp/tftp.c	(revision 42190)
@@ -591,9 +591,10 @@
     {
         if (pTftpSession->OptionBlkSize.u64Value > UINT16_MAX)
-            return -1;
+            rc = VERR_INVALID_PARAMETER;
         else
             rc = tftpAddOptionToOACK(pData, m, "blksize", pTftpSession->OptionBlkSize.u64Value);
     }
-    if (pTftpSession->OptionTSize.fRequested)
+    if (   RT_SUCCESS(rc)
+        && pTftpSession->OptionTSize.fRequested)
         rc = tftpAddOptionToOACK(pData, m, "tsize", pTftpSession->OptionTSize.u64Value);