diff --git a/CRM/Core/Config/Defaults.php b/CRM/Core/Config/Defaults.php
index a017330e9711..8335886a6a9d 100644
--- a/CRM/Core/Config/Defaults.php
+++ b/CRM/Core/Config/Defaults.php
@@ -81,6 +81,7 @@ public function setCoreVariables() {
   public static function formatUnitSize($size, $checkForPostMax = FALSE) {
     if ($size) {
       $last = strtolower($size{strlen($size) - 1});
+      $size = (int) $size;
       switch ($last) {
         // The 'G' modifier is available since PHP 5.1.0
 
diff --git a/tests/phpunit/CRM/Core/Config/DefaultsTest.php b/tests/phpunit/CRM/Core/Config/DefaultsTest.php
new file mode 100644
index 000000000000..b47a7d43ee34
--- /dev/null
+++ b/tests/phpunit/CRM/Core/Config/DefaultsTest.php
@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * Class CRM_Core_Config_DefaultsTest
+ */
+class CRM_Core_Config_DefaultsTest extends CiviUnitTestCase {
+
+
+  public function sizeCases() {
+    $cases = [];
+    $cases[] = ['20M', '20971520'];
+    $cases[] = ['40G', '42949672960'];
+    return $cases;
+  }
+
+  /**
+   * @param $size
+   * @param $expectedValue
+   * @dataProvider sizeCases
+   */
+  public function testFormatUnitSize($size, $expectedValue) {
+    $this->assertEquals($expectedValue, CRM_Core_Config_Defaults::formatUnitSize($size));
+  }
+
+}