diff --git a/CRM/Dedupe/Merger.php b/CRM/Dedupe/Merger.php
index 12c3903d8c28..e8eeb347e740 100644
--- a/CRM/Dedupe/Merger.php
+++ b/CRM/Dedupe/Merger.php
@@ -39,25 +39,25 @@ class CRM_Dedupe_Merger {
    * @return array
    */
   public static function relTables() {
-    static $relTables;
 
-    // Setting these merely prevents enotices - but it may be more appropriate not to add the user table below
-    // if the url can't be retrieved. A more standardised way to retrieve them is.
-    // CRM_Core_Config::singleton()->userSystem->getUserRecordUrl() - however that function takes a contact_id &
-    // we may need a different function when it is not known.
-    $title = $userRecordUrl = '';
+    if (!isset(Civi::$statics[__CLASS__]['relTables'])) {
 
-    $config = CRM_Core_Config::singleton();
-    if ($config->userSystem->is_drupal) {
-      $userRecordUrl = CRM_Utils_System::url('user/%ufid');
-      $title = ts('%1 User: %2; user id: %3', array(1 => $config->userFramework, 2 => '$ufname', 3 => '$ufid'));
-    }
-    elseif ($config->userFramework == 'Joomla') {
-      $userRecordUrl = $config->userSystem->getVersion() > 1.5 ? $config->userFrameworkBaseURL . "index.php?option=com_users&view=user&task=user.edit&id=" . '%ufid' : $config->userFrameworkBaseURL . "index2.php?option=com_users&view=user&task=edit&id[]=" . '%ufid';
-      $title = ts('%1 User: %2; user id: %3', array(1 => $config->userFramework, 2 => '$ufname', 3 => '$ufid'));
-    }
+      // Setting these merely prevents enotices - but it may be more appropriate not to add the user table below
+      // if the url can't be retrieved. A more standardised way to retrieve them is.
+      // CRM_Core_Config::singleton()->userSystem->getUserRecordUrl() - however that function takes a contact_id &
+      // we may need a different function when it is not known.
+      $title = $userRecordUrl = '';
+
+      $config = CRM_Core_Config::singleton();
+      if ($config->userSystem->is_drupal) {
+        $userRecordUrl = CRM_Utils_System::url('user/%ufid');
+        $title = ts('%1 User: %2; user id: %3', array(1 => $config->userFramework, 2 => '$ufname', 3 => '$ufid'));
+      }
+      elseif ($config->userFramework == 'Joomla') {
+        $userRecordUrl = $config->userSystem->getVersion() > 1.5 ? $config->userFrameworkBaseURL . "index.php?option=com_users&view=user&task=user.edit&id=" . '%ufid' : $config->userFrameworkBaseURL . "index2.php?option=com_users&view=user&task=edit&id[]=" . '%ufid';
+        $title = ts('%1 User: %2; user id: %3', array(1 => $config->userFramework, 2 => '$ufname', 3 => '$ufid'));
+      }
 
-    if (!$relTables) {
       $relTables = array(
         'rel_table_contributions' => array(
           'title' => ts('Contributions'),
@@ -155,8 +155,12 @@ public static function relTables() {
 
       // Allow hook_civicrm_merge() to adjust $relTables
       CRM_Utils_Hook::merge('relTables', $relTables);
+
+      // Cache the results in a static variable
+      Civi::$statics[__CLASS__]['relTables'] = $relTables;
     }
-    return $relTables;
+
+    return Civi::$statics[__CLASS__]['relTables'];
   }
 
   /**
@@ -273,11 +277,12 @@ public static function locTables() {
    * We treat multi-valued custom sets as "related tables" similar to activities, contributions, etc.
    * @param string $request
    *   'relTables' or 'cidRefs'.
+   * @return array
    * @see CRM-13836
    */
   public static function getMultiValueCustomSets($request) {
-    static $data = NULL;
-    if ($data === NULL) {
+
+    if (!isset(Civi::$statics[__CLASS__]['multiValueCustomSets'])) {
       $data = array(
         'relTables' => array(),
         'cidRefs' => array(),
@@ -296,8 +301,12 @@ public static function getMultiValueCustomSets($request) {
           'url' => CRM_Utils_System::url('civicrm/contact/view', 'reset=1&force=1&cid=$cid' . $urlSuffix),
         );
       }
+
+      // Store the result in a static variable cache
+      Civi::$statics[__CLASS__]['multiValueCustomSets'] = $data;
     }
-    return $data[$request];
+
+    return Civi::$statics[__CLASS__]['multiValueCustomSets'][$request];
   }
 
   /**
@@ -467,12 +476,15 @@ public static function moveContactBelongings($mainId, $otherId, $tables = FALSE,
 
     $mainId = (int) $mainId;
     $otherId = (int) $otherId;
+    $multi_value_tables = array_keys(CRM_Dedupe_Merger::getMultiValueCustomSets('cidRefs'));
 
     $sqls = array();
     foreach ($affected as $table) {
-      // skipping non selected custom table's value migration
-      if ($customTableToCopyFrom !== NULL && in_array($table, $customTables) && !in_array($table, $customTableToCopyFrom)) {
-        continue;
+      // skipping non selected single-value custom table's value migration
+      if (!in_array($table, $multi_value_tables)) {
+        if ($customTableToCopyFrom !== NULL && in_array($table, $customTables) && !in_array($table, $customTableToCopyFrom)) {
+          continue;
+        }
       }
 
       // Call custom processing function for objects that require it
diff --git a/tests/phpunit/CRM/Dedupe/MergerTest.php b/tests/phpunit/CRM/Dedupe/MergerTest.php
index 4db2dbd9e59c..022875fbe819 100644
--- a/tests/phpunit/CRM/Dedupe/MergerTest.php
+++ b/tests/phpunit/CRM/Dedupe/MergerTest.php
@@ -549,6 +549,14 @@ public function testMigrationOfUnselectedCustomDataOnEmptyCustomRecord() {
     $createGroup  = $this->setupCustomGroupForIndividual();
     $customField1 = $this->setupCustomField('TestField', $createGroup);
 
+    // Create multi-value custom field
+    $multiGroup = $this->CustomGroupMultipleCreateByParams();
+    $multiField = $this->customFieldCreate(array(
+      'custom_group_id' => $multiGroup['id'],
+      'label' => 'field_1' . $multiGroup['id'],
+      'in_selector' => 1,
+    ));
+
     // Contacts setup
     $this->setupMatchData();
     $originalContactID = $this->contacts[0]['id'];
@@ -558,17 +566,24 @@ public function testMigrationOfUnselectedCustomDataOnEmptyCustomRecord() {
     $this->callAPISuccess('Contact', 'create', array(
       'id' => $duplicateContactID,
       "custom_{$customField1['id']}" => 'abc',
+      "custom_{$multiField['id']}" => 'def',
     ));
     $this->assertCustomFieldValue($duplicateContactID, 'abc', "custom_{$customField1['id']}");
+    $this->assertCustomFieldValue($duplicateContactID, 'def', "custom_{$multiField['id']}");
 
+    // Merge, and ensure that no value was migrated
     $this->mergeContacts($originalContactID, $duplicateContactID, array(
       "move_custom_{$customField1['id']}" => NULL,
+      "move_rel_table_custom_{$multiGroup['id']}" => NULL,
     ));
     $this->assertCustomFieldValue($originalContactID, '', "custom_{$customField1['id']}");
+    $this->assertCustomFieldValue($originalContactID, '', "custom_{$multiField['id']}");
 
     // cleanup created custom set
     $this->callAPISuccess('CustomField', 'delete', array('id' => $customField1['id']));
     $this->callAPISuccess('CustomGroup', 'delete', array('id' => $createGroup['id']));
+    $this->callAPISuccess('CustomField', 'delete', array('id' => $multiField['id']));
+    $this->callAPISuccess('CustomGroup', 'delete', array('id' => $multiGroup['id']));
   }
 
   /**
@@ -583,6 +598,14 @@ public function testMigrationOfSomeCustomDataOnEmptyCustomRecord() {
     $customField1 = $this->setupCustomField('Test1', $createGroup);
     $customField2 = $this->setupCustomField('Test2', $createGroup);
 
+    // Create multi-value custom field
+    $multiGroup = $this->CustomGroupMultipleCreateByParams();
+    $multiField = $this->customFieldCreate(array(
+      'custom_group_id' => $multiGroup['id'],
+      'label' => 'field_1' . $multiGroup['id'],
+      'in_selector' => 1,
+    ));
+
     // Contacts setup
     $this->setupMatchData();
     $originalContactID = $this->contacts[0]['id'];
@@ -593,22 +616,28 @@ public function testMigrationOfSomeCustomDataOnEmptyCustomRecord() {
       'id' => $duplicateContactID,
       "custom_{$customField1['id']}" => 'abc',
       "custom_{$customField2['id']}" => 'def',
+      "custom_{$multiField['id']}" => 'ghi',
     ));
     $this->assertCustomFieldValue($duplicateContactID, 'abc', "custom_{$customField1['id']}");
     $this->assertCustomFieldValue($duplicateContactID, 'def', "custom_{$customField2['id']}");
+    $this->assertCustomFieldValue($duplicateContactID, 'ghi', "custom_{$multiField['id']}");
 
     // Perform merge
     $this->mergeContacts($originalContactID, $duplicateContactID, array(
       "move_custom_{$customField1['id']}" => NULL,
       "move_custom_{$customField2['id']}" => 'def',
+      "move_rel_table_custom_{$multiGroup['id']}" => '1',
     ));
     $this->assertCustomFieldValue($originalContactID, '', "custom_{$customField1['id']}");
     $this->assertCustomFieldValue($originalContactID, 'def', "custom_{$customField2['id']}");
+    $this->assertCustomFieldValue($originalContactID, 'ghi', "custom_{$multiField['id']}");
 
     // cleanup created custom set
     $this->callAPISuccess('CustomField', 'delete', array('id' => $customField1['id']));
     $this->callAPISuccess('CustomField', 'delete', array('id' => $customField2['id']));
     $this->callAPISuccess('CustomGroup', 'delete', array('id' => $createGroup['id']));
+    $this->callAPISuccess('CustomField', 'delete', array('id' => $multiField['id']));
+    $this->callAPISuccess('CustomGroup', 'delete', array('id' => $multiGroup['id']));
   }
 
   /**