diff --git a/idle_scan.cc b/idle_scan.cc
index 8b10e9ad6..195048995 100644
--- a/idle_scan.cc
+++ b/idle_scan.cc
@@ -226,7 +226,7 @@ static int ipid_proxy_probe(struct idle_proxy_info *proxy, int *probes_sent,
 	    }
 	    else if (o.debugging > 1) {
 	      error("Received unexpected response packet from %s during IP ID zombie probing:", inet_ntoa(ip->ip_src));
-	      readtcppacket( (unsigned char *) ip,ntohs(ip->ip_len));
+	      readtcppacket( (unsigned char *) ip,MIN(ntohs(ip->ip_len), bytes));
 	    }
 	    continue;
 	  }