diff --git a/CRM/Activity/Import/Parser.php b/CRM/Activity/Import/Parser.php
index 9669df0ff3a7..6e4d290bf594 100644
--- a/CRM/Activity/Import/Parser.php
+++ b/CRM/Activity/Import/Parser.php
@@ -59,7 +59,7 @@ abstract class CRM_Activity_Import_Parser extends CRM_Import_Parser {
   public function run(
     array $fileName,
     $separator,
-    &$mapper,
+    $mapper,
     $skipColumnHeader = FALSE,
     $mode = self::MODE_PREVIEW,
     $onDuplicate = self::DUPLICATE_SKIP,
diff --git a/CRM/Contribute/Import/Parser/Contribution.php b/CRM/Contribute/Import/Parser/Contribution.php
index f08b2104422d..b7ce5392c6dd 100644
--- a/CRM/Contribute/Import/Parser/Contribution.php
+++ b/CRM/Contribute/Import/Parser/Contribution.php
@@ -152,7 +152,7 @@ public function __construct(&$mapperKeys, $mapperSoftCredit = [], $mapperPhoneTy
   public function run(
     $fileName,
     $separator,
-    &$mapper,
+    $mapper,
     $skipColumnHeader = FALSE,
     $mode = self::MODE_PREVIEW,
     $contactType = self::CONTACT_INDIVIDUAL,
diff --git a/CRM/Custom/Import/Parser.php b/CRM/Custom/Import/Parser.php
index 91847a14725d..7ac8b810bfea 100644
--- a/CRM/Custom/Import/Parser.php
+++ b/CRM/Custom/Import/Parser.php
@@ -59,7 +59,7 @@ abstract class CRM_Custom_Import_Parser extends CRM_Import_Parser {
   public function run(
     $fileName,
     $separator,
-    &$mapper,
+    $mapper,
     $skipColumnHeader = FALSE,
     $mode = self::MODE_PREVIEW,
     $contactType = self::CONTACT_INDIVIDUAL,
diff --git a/CRM/Event/Import/Parser.php b/CRM/Event/Import/Parser.php
index ee9f8ba17982..ee1ddff787d6 100644
--- a/CRM/Event/Import/Parser.php
+++ b/CRM/Event/Import/Parser.php
@@ -61,7 +61,7 @@ abstract class CRM_Event_Import_Parser extends CRM_Import_Parser {
   public function run(
     $fileName,
     $separator,
-    &$mapper,
+    $mapper,
     $skipColumnHeader = FALSE,
     $mode = self::MODE_PREVIEW,
     $contactType = self::CONTACT_INDIVIDUAL,
diff --git a/CRM/Import/Form/DataSource.php b/CRM/Import/Form/DataSource.php
index e2e3e2d6f73d..36de82c71fdf 100644
--- a/CRM/Import/Form/DataSource.php
+++ b/CRM/Import/Form/DataSource.php
@@ -150,7 +150,7 @@ protected function submitFileForMapping($parserClassName, $entity = NULL) {
     $parser->setMaxLinesToProcess(100);
     $parser->run($fileName,
       $separator,
-      $mapper,
+      [],
       $skipColumnHeader,
       CRM_Import_Parser::MODE_MAPFIELD,
       $this->get('contactType')