diff --git a/src/SearchResults/index.js b/src/SearchResults/index.js
index 3b585b84e..ef516bf13 100644
--- a/src/SearchResults/index.js
+++ b/src/SearchResults/index.js
@@ -3,7 +3,6 @@
 var compact = require('lodash/compact');
 var findIndex = require('lodash/findIndex');
 
-var sumBy = require('lodash/sumBy');
 var find = require('lodash/find');
 var orderBy = require('lodash/orderBy');
 
@@ -286,7 +285,11 @@ function SearchResults(state, results) {
    * sum of the processing time of all the queries
    * @member {number}
    */
-  this.processingTimeMS = sumBy(results, 'processingTimeMS');
+  this.processingTimeMS = results.reduce(function(sum, result) {
+    return result.processingTimeMS === undefined
+      ? sum
+      : sum + result.processingTimeMS;
+  }, 0);
   /**
    * The position if the position was guessed by IP.
    * @member {string}
diff --git a/test/spec/SearchResults/initialization.js b/test/spec/SearchResults/initialization.js
new file mode 100644
index 000000000..982779ee5
--- /dev/null
+++ b/test/spec/SearchResults/initialization.js
@@ -0,0 +1,30 @@
+'use strict';
+
+var SearchParameters = require('../../../src/SearchParameters');
+var SearchResults = require('../../../src/SearchResults');
+
+test('processingTime should be the sum of all individual times', function() {
+  var result = new SearchResults(new SearchParameters(), [
+    {
+      processingTimeMS: 1
+    },
+    {
+      processingTimeMS: 1
+    }
+  ]);
+
+  expect(result.processingTimeMS).toBe(2);
+});
+
+test('processingTime should ignore undefined', function() {
+  var result = new SearchResults(new SearchParameters(), [
+    {
+      processingTimeMS: undefined
+    },
+    {
+      processingTimeMS: 1
+    }
+  ]);
+
+  expect(result.processingTimeMS).toBe(1);
+});