diff --git a/src/internal.c b/src/internal.c
index be2c5d83..d47d906c 100644
--- a/src/internal.c
+++ b/src/internal.c
@@ -2215,7 +2215,8 @@ int wolfSSH_SendPacket(WOLFSSH* ssh)
 
        sent = ssh->ctx->ioSendCb(ssh,
                                ssh->outputBuffer.buffer + ssh->outputBuffer.idx,
-                               ssh->outputBuffer.length, ssh->ioWriteCtx);
+                               ssh->outputBuffer.length - ssh->outputBuffer.idx,
+                               ssh->ioWriteCtx);
 
         if (sent < 0) {
             switch (sent) {