diff --git a/modules/tracker/controllers/components/ApiComponent.php b/modules/tracker/controllers/components/ApiComponent.php
index 632fbc78b..78974f2ce 100644
--- a/modules/tracker/controllers/components/ApiComponent.php
+++ b/modules/tracker/controllers/components/ApiComponent.php
@@ -247,7 +247,7 @@ public function scalarAdd($args)
         if (isset($args['unit'])) {
             $unit = $args['unit'];
         } else {
-            $unit = null;
+            $unit = false;
         }
         /** @var Tracker_TrendModel $trendModel */
         $trendModel = MidasLoader::loadModel('Trend', 'tracker');
diff --git a/modules/tracker/models/base/TrendModelBase.php b/modules/tracker/models/base/TrendModelBase.php
index 91ec91988..b49a32914 100644
--- a/modules/tracker/models/base/TrendModelBase.php
+++ b/modules/tracker/models/base/TrendModelBase.php
@@ -75,17 +75,17 @@ public function __construct()
     }
 
     /**
-     * Return the trend DAO that matches the given the producer id, metric name, and associated items.
+     * Return the trend DAO that matches the given the producer id, metric name, associated items, and unit.
      *
      * @param int $producerId producer id
      * @param string $metricName metric name
      * @param null|int $configItemId configuration item id
      * @param null|int $testDatasetId test dataset item id
      * @param null|int $truthDatasetId truth dataset item id
-     * @param null|string $unit scalar value unit
+     * @param false|string $unit (Optional) scalar value unit, defaults to false
      * @return false|Tracker_TrendDao trend DAO or false if none exists
      */
-    abstract public function getMatch($producerId, $metricName, $configItemId, $testDatasetId, $truthDatasetId, $unit);
+    abstract public function getMatch($producerId, $metricName, $configItemId, $testDatasetId, $truthDatasetId, $unit = false);
 
     /**
      * Return the trend DAOs that match the given associative array of database columns and values.
@@ -129,7 +129,7 @@ public function save($trendDao)
     }
 
     /**
-     * Return the trend DAO that matches the given producer id, metric name, and associated items if it exists.
+     * Return the trend DAO that matches the given producer id, metric name, associated items, and unit, if the trend exists.
      * Otherwise, create the trend DAO.
      *
      * @param int $producerId producer id
@@ -137,10 +137,10 @@ public function save($trendDao)
      * @param null|int $configItemId configuration item id
      * @param null|int $testDatasetId test dataset item id
      * @param null|int $truthDatasetId truth dataset item id
-     * @param null|string $unit scalar value unit
+     * @param false|string $unit (Optional) scalar value unit, defaults to false
      * @return Tracker_TrendDao trend DAO
      */
-    public function createIfNeeded($producerId, $metricName, $configItemId, $testDatasetId, $truthDatasetId, $unit)
+    public function createIfNeeded($producerId, $metricName, $configItemId, $testDatasetId, $truthDatasetId, $unit = false)
     {
         $trendDao = $this->getMatch($producerId, $metricName, $configItemId, $testDatasetId, $truthDatasetId, $unit);
 
@@ -150,7 +150,7 @@ public function createIfNeeded($producerId, $metricName, $configItemId, $testDat
             $trendDao->setProducerId($producerId);
             $trendDao->setMetricName($metricName);
             $trendDao->setDisplayName($metricName);
-            if (is_null($unit)) {
+            if ($unit === false) {
                 $unit = '';
             }
             $trendDao->setUnit($unit);
diff --git a/modules/tracker/models/pdo/TrendModel.php b/modules/tracker/models/pdo/TrendModel.php
index 88db47232..c8d64dc2f 100644
--- a/modules/tracker/models/pdo/TrendModel.php
+++ b/modules/tracker/models/pdo/TrendModel.php
@@ -24,17 +24,17 @@
 class Tracker_TrendModel extends Tracker_TrendModelBase
 {
     /**
-     * Return the trend DAO that matches the given the producer id, metric name, and associated items.
+     * Return the trend DAO that matches the given the producer id, metric name, associated items, and unit.
      *
      * @param int $producerId producer id
      * @param string $metricName metric name
      * @param null|int $configItemId configuration item id
      * @param null|int $testDatasetId test dataset item id
      * @param null|int $truthDatasetId truth dataset item id
-     * @param null|string $unit scalar value unit
+     * @param false|string $unit (Optional) scalar value unit, defaults to false
      * @return false|Tracker_TrendDao trend DAO or false if none exists
      */
-    public function getMatch($producerId, $metricName, $configItemId, $testDatasetId, $truthDatasetId, $unit)
+    public function getMatch($producerId, $metricName, $configItemId, $testDatasetId, $truthDatasetId, $unit = false)
     {
         $sql = $this->database->select()->setIntegrityCheck(false)->where('producer_id = ?', $producerId)->where(
             'metric_name = ?',
@@ -59,7 +59,7 @@ public function getMatch($producerId, $metricName, $configItemId, $testDatasetId
             $sql->where('test_dataset_id = ?', $testDatasetId);
         }
 
-        if (!is_null($unit) && ($unit !== '')) {
+        if ($unit !== false) {
             $sql->where('unit = ?', $unit);
         }
 
diff --git a/modules/tracker/tests/controllers/ApiControllerTest.php b/modules/tracker/tests/controllers/ApiControllerTest.php
index 550837060..6788a6325 100644
--- a/modules/tracker/tests/controllers/ApiControllerTest.php
+++ b/modules/tracker/tests/controllers/ApiControllerTest.php
@@ -75,10 +75,10 @@ public function testUploadScalarWithSubmission()
      * @param string $uuid the uuid of the submission
      * @param string $metric the metric name of the trend
      * @param float $value the scalar value
-     * @param string $unit the unit of the trend, defaults to false
+     * @param false|string $unit (Optional) the unit of the trend, defaults to false
      * @return mixed response object from the API
      */
-    protected function _submitScalar($token, $uuid, $metric, $value, $unit = false)
+    private function _submitScalar($token, $uuid, $metric, $value, $unit = false)
     {
         $this->resetAll();
         $this->params['method'] = 'midas.tracker.scalar.add';