diff --git a/include/Flow.h b/include/Flow.h
index fd71badb51..c8db0fa0e0 100644
--- a/include/Flow.h
+++ b/include/Flow.h
@@ -166,7 +166,7 @@ class Flow : public GenericHashEntry {
   struct timeval c2sFirstGoodputTime;
   float rttSec, applLatencyMsec;
 
-  InterarrivalStats cli2srvPktTime, srv2cliPktTime;
+  InterarrivalStats *cli2srvPktTime, *srv2cliPktTime;
   
   /* Counter values at last host update */
   struct {
@@ -211,7 +211,7 @@ class Flow : public GenericHashEntry {
   bool checkTor(char *hostname);
   void setBittorrentHash(char *hash);
   bool isLowGoodput();
-  void updatePacketStats(InterarrivalStats *stats, const struct timeval *when);
+  static void updatePacketStats(InterarrivalStats *stats, const struct timeval *when);
   void dumpPacketStats(lua_State* vm, bool cli2srv_direction);
   bool isReadyToBeMarkedAsIdle();
   bool isBlacklistedFlow() const;
@@ -466,9 +466,9 @@ class Flow : public GenericHashEntry {
   inline float getCli2SrvMaxThpt() { return(rttSec ? ((float)(cli2srv_window*8)/rttSec) : 0); }
   inline float getSrv2CliMaxThpt() { return(rttSec ? ((float)(srv2cli_window*8)/rttSec) : 0); }
 
-  inline InterarrivalStats* getCli2SrvIATStats()   { return(&cli2srvPktTime); }
-  inline InterarrivalStats* getSrv2CliIATStats()   { return(&srv2cliPktTime); }
-  
+  inline InterarrivalStats* getCli2SrvIATStats() const { return cli2srvPktTime; }
+  inline InterarrivalStats* getSrv2CliIATStats() const { return srv2cliPktTime; }
+
   bool isIdleFlow();
   inline bool isTCPEstablished() const { return (!isTCPClosed() && !isTCPReset()
 						 && ((src2dst_tcp_flags & (TH_SYN | TH_ACK)) == (TH_SYN | TH_ACK))
diff --git a/scripts/lua/flow_details.lua b/scripts/lua/flow_details.lua
index b4dc2914d1..26a8f28e2e 100644
--- a/scripts/lua/flow_details.lua
+++ b/scripts/lua/flow_details.lua
@@ -585,7 +585,6 @@ print [[
 if(flow == nil) then
    print('<div class=\"alert alert-danger\"><i class="fa fa-warning fa-lg"></i> '..i18n("flow_details.flow_cannot_be_found_message")..' '.. purgedErrorString()..'</div>')
 else
-
    if isAdministrator() then
       if(_POST["drop_flow_policy"] == "true") then
 	 interface.dropFlowTraffic(tonumber(flow_key))
@@ -630,7 +629,7 @@ else
 	 print(i18n("flow_details.ssl_old_protocol_version"))
       end
    end
-   
+
    if(ifstats.inline) then
       if(flow["verdict.pass"]) then
 	 print('<form class="form-inline pull-right" style="margin-bottom: 0px;" method="post">')
@@ -792,8 +791,8 @@ else
       print("<tr><th width=30%>"..i18n("flow_details.application_latency").."</th><td colspan=2>"..msToTime(flow["tcp.appl_latency"]).."</td></tr>\n")
    end
 
-    if(not string.starts(ifname, "nf:")) then
-       if((flow["cli2srv.packets"] > 1) and (flow["interarrival.cli2srv"]["max"] > 0)) then
+   if(not string.starts(ifname, "nf:")) then
+      if flow["cli2srv.packets"] > 1 and flow["interarrival.cli2srv"] and flow["interarrival.cli2srv"]["max"] > 0 then
 	  print("<tr><th width=30%")
 	  if(flow["flow.idle"] == true) then print(" rowspan=2") end
 	  print(">"..i18n("flow_details.packet_inter_arrival_time").."</th><td nowrap>"..i18n("client").." <i class=\"fa fa-arrow-right\"></i> "..i18n("server")..": ")
diff --git a/src/Flow.cpp b/src/Flow.cpp
index b1a80d00e3..6bc1951c5a 100644
--- a/src/Flow.cpp
+++ b/src/Flow.cpp
@@ -155,6 +155,15 @@ Flow::Flow(NetworkInterface *_iface,
   if(!iface->isPacketInterface())
     last_update_time.tv_sec = (long)first_seen;
 
+  if(iface->isPacketInterface() && !iface->isSampledTraffic()) {
+    cli2srvPktTime = new (std::nothrow) InterarrivalStats();
+    srv2cliPktTime = new (std::nothrow) InterarrivalStats();
+  } else {
+    cli2srvPktTime = NULL;
+    srv2cliPktTime = NULL;
+  }
+    
+
 #ifdef NTOPNG_PRO
 #ifndef HAVE_NEDGE
   trafficProfile = NULL;
@@ -237,6 +246,9 @@ Flow::~Flow() {
   if(cli_ebpf) delete cli_ebpf;
   if(srv_ebpf) delete srv_ebpf;
 
+  if(cli2srvPktTime) delete cli2srvPktTime;
+  if(srv2cliPktTime) delete srv2cliPktTime;
+
   if(isHTTP()) {
     if(protos.http.last_method) free(protos.http.last_method);
     if(protos.http.last_url)    free(protos.http.last_url);
@@ -2589,7 +2601,8 @@ bool Flow::update_partial_traffic_stats_db_dump() {
 /* *************************************** */
 
 void Flow::updatePacketStats(InterarrivalStats *stats, const struct timeval *when) {
-  stats->updatePacketStats((struct timeval*)when);
+  if(stats)
+    stats->updatePacketStats((struct timeval*)when);
 }
 
 /* *************************************** */
@@ -2597,18 +2610,20 @@ void Flow::updatePacketStats(InterarrivalStats *stats, const struct timeval *whe
 void Flow::dumpPacketStats(lua_State* vm, bool cli2srv_direction) {
   InterarrivalStats *s = cli2srv_direction ? getCli2SrvIATStats() : getSrv2CliIATStats();
 
-  lua_newtable(vm);
+  if(s) {
+    lua_newtable(vm);
   
-  lua_push_float_table_entry(vm, "min",    (float)s->getMin());
-  lua_push_float_table_entry(vm, "max",    (float)s->getMax());
-  lua_push_float_table_entry(vm, "avg",    s->getAvg());
-  lua_push_float_table_entry(vm, "stddev", s->getStdDev());
+    lua_push_uint64_table_entry(vm, "min",   s->getMin());
+    lua_push_uint64_table_entry(vm, "max",   s->getMax());
+    lua_push_float_table_entry(vm, "avg",    s->getAvg());
+    lua_push_float_table_entry(vm, "stddev", s->getStdDev());
 
-  // ntop->getTrace()->traceEvent(TRACE_NORMAL, "%u / %.1f / %u", s->getMin(), s->getAvg(), s->getMax());
+    // ntop->getTrace()->traceEvent(TRACE_NORMAL, "%u / %.1f / %u", s->getMin(), s->getAvg(), s->getMax());
 			       
-  lua_pushstring(vm, cli2srv_direction ? "interarrival.cli2srv" : "interarrival.srv2cli");
-  lua_insert(vm, -2);
-  lua_settable(vm, -3);
+    lua_pushstring(vm, cli2srv_direction ? "interarrival.cli2srv" : "interarrival.srv2cli");
+    lua_insert(vm, -2);
+    lua_settable(vm, -3);
+  }
 }
 
 /* *************************************** */