diff --git a/inc/line.class.php b/inc/line.class.php
index bc69700..9a34adc 100644
--- a/inc/line.class.php
+++ b/inc/line.class.php
@@ -284,7 +284,7 @@ static function install(Migration $migration) {
 
       $default_charset = DBConnection::getDefaultCharset();
       $default_collation = DBConnection::getDefaultCollation();
-      $default_key_sign = method_exists('DBConnection', 'getDefaultPrimaryKeySignOption') ? DBConnection::getDefaultPrimaryKeySignOption() : '';
+      $default_key_sign = DBConnection::getDefaultPrimaryKeySignOption();
 
       $table = self::getTable();
       if (!$DB->tableExists($table)) {
diff --git a/inc/phone.class.php b/inc/phone.class.php
index 242eaed..884c710 100644
--- a/inc/phone.class.php
+++ b/inc/phone.class.php
@@ -345,7 +345,7 @@ static function install(Migration $migration) {
 
       $default_charset = DBConnection::getDefaultCharset();
       $default_collation = DBConnection::getDefaultCollation();
-      $default_key_sign = method_exists('DBConnection', 'getDefaultPrimaryKeySignOption') ? DBConnection::getDefaultPrimaryKeySignOption() : '';
+      $default_key_sign = DBConnection::getDefaultPrimaryKeySignOption();
 
       $table = self::getTable();
       if (!$DB->tableExists($table)) {
diff --git a/inc/phone_line.class.php b/inc/phone_line.class.php
index e395ff8..8f34556 100644
--- a/inc/phone_line.class.php
+++ b/inc/phone_line.class.php
@@ -386,7 +386,7 @@ static function install(Migration $migration) {
 
       $default_charset = DBConnection::getDefaultCharset();
       $default_collation = DBConnection::getDefaultCollation();
-      $default_key_sign = method_exists('DBConnection', 'getDefaultPrimaryKeySignOption') ? DBConnection::getDefaultPrimaryKeySignOption() : '';
+      $default_key_sign = DBConnection::getDefaultPrimaryKeySignOption();
 
       $table = self::getTable();
       if (!$DB->tableExists($table)) {