diff --git a/hw/rtl8139.c b/hw/rtl8139.c
index 05b8e1e3d7..be4bc6a947 100644
--- a/hw/rtl8139.c
+++ b/hw/rtl8139.c
@@ -2061,13 +2061,12 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s)
             s->cplus_txbuffer_len);
     }
 
-    while (s->cplus_txbuffer && s->cplus_txbuffer_offset + txsize >= s->cplus_txbuffer_len)
+    if (s->cplus_txbuffer_offset + txsize >= s->cplus_txbuffer_len)
     {
-        s->cplus_txbuffer_len += CP_TX_BUFFER_SIZE;
-        s->cplus_txbuffer = g_realloc(s->cplus_txbuffer, s->cplus_txbuffer_len);
-
-        DPRINTF("+++ C+ mode transmission buffer space changed to %d\n",
-            s->cplus_txbuffer_len);
+        /* The spec didn't tell the maximum size, stick to CP_TX_BUFFER_SIZE */
+        txsize = s->cplus_txbuffer_len - s->cplus_txbuffer_offset;
+        DPRINTF("+++ C+ mode transmission buffer overrun, truncated descriptor"
+                "length to %d\n", txsize);
     }
 
     if (!s->cplus_txbuffer)