diff --git a/scan_engine.cc b/scan_engine.cc
index a05904367..7f040b324 100644
--- a/scan_engine.cc
+++ b/scan_engine.cc
@@ -826,7 +826,7 @@ void UltraProbe::setIP(u8 *ippacket, u32 len, const probespec *pspec) {
     data = ipv6_get_data(ip6, &len, &hdr);
     assert(data != NULL);
     assert(len == (u32) ntohs(ip6->ip6_plen));
-    probes.IP.ipid = ntohs(ip6->ip6_flow & IP6_FLOWLABEL_MASK) & 0xFFFF;
+    probes.IP.ipid = ntohl(ip6->ip6_flow & IP6_FLOWLABEL_MASK) & 0xFFFF;
     hdr = ip6->ip6_nxt;
   } else {
     fatal("Bogus packet passed to %s -- only IP packets allowed", __func__);