diff --git a/CRM/Case/BAO/Case.php b/CRM/Case/BAO/Case.php
index 1b1340a9ef17..f947784c068b 100644
--- a/CRM/Case/BAO/Case.php
+++ b/CRM/Case/BAO/Case.php
@@ -2084,28 +2084,6 @@ public static function mergeCases(
           continue;
         }
 
-        // CRM-11662 Copy Case custom data
-        $extends = array('case');
-        $groupTree = CRM_Core_BAO_CustomGroup::getGroupDetail(NULL, NULL, $extends);
-        if ($groupTree) {
-          foreach ($groupTree as $groupID => $group) {
-            $table[$groupTree[$groupID]['table_name']] = array('entity_id');
-            foreach ($group['fields'] as $fieldID => $field) {
-              $table[$groupTree[$groupID]['table_name']][] = $groupTree[$groupID]['fields'][$fieldID]['column_name'];
-            }
-          }
-
-          foreach ($table as $tableName => $tableColumns) {
-            $insert = 'INSERT INTO ' . $tableName . ' (' . implode(', ', $tableColumns) . ') ';
-            $tableColumns[0] = $mainCaseId;
-            $select = 'SELECT ' . implode(', ', $tableColumns);
-            $from = ' FROM ' . $tableName;
-            $where = " WHERE {$tableName}.entity_id = {$otherCaseId}";
-            $query = $insert . $select . $from . $where;
-            $dao = CRM_Core_DAO::executeQuery($query);
-          }
-        }
-
         $mainCaseIds[] = $mainCaseId;
         //insert record for case contact.
         $otherCaseContact = new CRM_Case_DAO_CaseContact();
diff --git a/tests/phpunit/CRM/Case/BAO/CaseTest.php b/tests/phpunit/CRM/Case/BAO/CaseTest.php
index fae0799d6999..1921c600ec7c 100644
--- a/tests/phpunit/CRM/Case/BAO/CaseTest.php
+++ b/tests/phpunit/CRM/Case/BAO/CaseTest.php
@@ -170,6 +170,68 @@ public function testRetrieveCaseIdsByContactId() {
     $this->assertEquals(array(1), $caseIds);
   }
 
+  /**
+   * Test that all custom files are migrated to new case when case is assigned to new client.
+   */
+  public function testCaseReassignForCustomFiles() {
+    $individual = $this->individualCreate();
+    $customGroup = $this->customGroupCreate(array(
+      'extends' => 'Case',
+    ));
+    $customGroup = $customGroup['values'][$customGroup['id']];
+
+    $customFileFieldA = $this->customFieldCreate(array(
+      'custom_group_id' => $customGroup['id'],
+      'html_type'       => 'File',
+      'is_active'       => 1,
+      'default_value'   => 'null',
+      'label'           => 'Custom File A',
+      'data_type'       => 'File',
+    ));
+
+    $customFileFieldB = $this->customFieldCreate(array(
+      'custom_group_id' => $customGroup['id'],
+      'html_type'       => 'File',
+      'is_active'       => 1,
+      'default_value'   => 'null',
+      'label'           => 'Custom File B',
+      'data_type'       => 'File',
+    ));
+
+    // Create two files to attach to the new case
+    $filepath = Civi::paths()->getPath('[civicrm.files]/custom');
+
+    CRM_Utils_File::createFakeFile($filepath, 'Bananas do not bend themselves without a little help.', 'i_bend_bananas.txt');
+    $fileA = $this->callAPISuccess('File', 'create', ['uri' => "$filepath/i_bend_bananas.txt"]);
+
+    CRM_Utils_File::createFakeFile($filepath, 'Wombats will bite your ankles if you run from them.', 'wombats_bite_your_ankles.txt');
+    $fileB = $this->callAPISuccess('File', 'create', ['uri' => "$filepath/wombats_bite_your_ankles.txt"]);
+
+    $caseObj = $this->createCase($individual);
+
+    $this->callAPISuccess('Case', 'create', array(
+      'id'                                => $caseObj->id,
+      'custom_' . $customFileFieldA['id'] => $fileA['id'],
+      'custom_' . $customFileFieldB['id'] => $fileB['id'],
+    ));
+
+    $reassignIndividual = $this->individualCreate();
+    $this->createLoggedInUser();
+    $newCase = CRM_Case_BAO_Case::mergeCases($reassignIndividual, $caseObj->id, $individual, NULL, TRUE);
+
+    $entityFiles = new CRM_Core_DAO_EntityFile();
+    $entityFiles->entity_id = $newCase[0];
+    $entityFiles->entity_table = $customGroup['table_name'];
+    $entityFiles->find();
+
+    $totalEntityFiles = 0;
+    while ($entityFiles->fetch()) {
+      $totalEntityFiles++;
+    }
+
+    $this->assertEquals(2, $totalEntityFiles, 'Two files should be attached with new case.');
+  }
+
   /**
    * FIXME: need to create an activity to run this test
    * function testGetCases() {
@@ -261,7 +323,8 @@ public function testCaseClosure() {
       'activity_date_time' => $now_date,
       'target_contact_id' => $client_id,
       'source_contact_id' => $loggedInUser,
-      'subject' => 'null', // yeah this is extra weird, but without it you get the wrong subject
+      // yeah this is extra weird, but without it you get the wrong subject
+      'subject' => 'null',
     ];
 
     $form->postProcess($actParams);