diff --git a/utils/tracers/ndn-l3-aggregate-tracer.cc b/utils/tracers/ndn-l3-aggregate-tracer.cc
index 52eb9f8..b64fc6b 100644
--- a/utils/tracers/ndn-l3-aggregate-tracer.cc
+++ b/utils/tracers/ndn-l3-aggregate-tracer.cc
@@ -187,8 +187,11 @@
 
   {
     std::map<Ptr<const Face>, boost::tuple<Stats, Stats> >::iterator stats = m_stats.find (Ptr<const Face> (0));
-    PRINTER ("SatisfiedInterests", m_satisfiedInterests);
-    PRINTER ("TimedOutInterests", m_timedOutInterests);
+    if (stats != m_stats.end ())
+      {
+        PRINTER ("SatisfiedInterests", m_satisfiedInterests);
+        PRINTER ("TimedOutInterests", m_timedOutInterests);
+      }
   }
 }
 
diff --git a/utils/tracers/ndn-l3-rate-tracer.cc b/utils/tracers/ndn-l3-rate-tracer.cc
index 88079b9..1e45f55 100644
--- a/utils/tracers/ndn-l3-rate-tracer.cc
+++ b/utils/tracers/ndn-l3-rate-tracer.cc
@@ -196,8 +196,11 @@
 
   {
     std::map<Ptr<const Face>, boost::tuple<Stats, Stats, Stats, Stats> >::iterator stats = m_stats.find (Ptr<const Face> (0));
-    PRINTER ("SatisfiedInterests", m_satisfiedInterests);
-    PRINTER ("TimedOutInterests", m_timedOutInterests);
+    if (stats != m_stats.end ())
+      {
+        PRINTER ("SatisfiedInterests", m_satisfiedInterests);
+        PRINTER ("TimedOutInterests", m_timedOutInterests);
+      }
   }
 }