diff --git a/lib/Interactor/TransactionAggregator.js b/lib/Interactor/TransactionAggregator.js
index 5bdc074c..b166cd6c 100644
--- a/lib/Interactor/TransactionAggregator.js
+++ b/lib/Interactor/TransactionAggregator.js
@@ -177,15 +177,6 @@ var TransactionAggregator = module.exports = function (pushInteractor) {
   this.mergeTrace = function (aggregated, trace) {
     if (!aggregated || !trace)
       return ;
-    if (!aggregated.variances)
-      aggregated.variances = [];
-
-    if (!aggregated.meta)
-      aggregated.meta = {
-        count: 0,
-        min: 100000,
-        max: 0
-      }
 
     // remove spans with startTime == endTime
     trace.spans = trace.spans.filter(function(span) {
@@ -195,6 +186,16 @@ var TransactionAggregator = module.exports = function (pushInteractor) {
     if (trace.spans.length == 0)
       return ;
 
+    // create data structure if needed
+    if (!aggregated.variances)
+      aggregated.variances = [];
+    if (!aggregated.meta)
+      aggregated.meta = {
+        count: 0,
+        min: 100000,
+        max: 0
+      }
+
     // compute duration of child spans
     trace.spans.forEach(function(span) {
       span.min = span.max = span.mean = Math.round(new Date(span.endTime) - new Date(span.startTime));
@@ -409,6 +410,10 @@ var TransactionAggregator = module.exports = function (pushInteractor) {
       Object.keys(routes).forEach(function(route_path) {
         var data = routes[route_path];
 
+        // hard check for invalid data
+        if (!data.variances || data.variances.length == 0)
+          return ;
+
         // get top 5 variances of the same route
         var variances = data.variances.sort(function(a, b) {
           return b.count - a.count;
@@ -422,6 +427,10 @@ var TransactionAggregator = module.exports = function (pushInteractor) {
         }
 
         variances.forEach(function (variance) {
+          // hard check for invalid data
+          if (!variance.spans || variance.spans.length == 0)
+            return ;
+
           // deep copy of variances data
           var tmp = fclone({
             spans: variance.spans,