diff --git a/install-dev/sql/db.sql b/install-dev/sql/db.sql
index 97438b149..08839e9a7 100644
--- a/install-dev/sql/db.sql
+++ b/install-dev/sql/db.sql
@@ -474,8 +474,6 @@ CREATE TABLE `PREFIX_customer_message_sync_imap` (
   KEY `md5_header_index` (`md5_header`(4))
 ) ENGINE=ENGINE_TYPE DEFAULT CHARSET=utf8;
 
-CREATE INDEX `md5_header_index` ON `PREFIX_customer_message_sync_imap` (md5_header(4));
-
 CREATE TABLE `PREFIX_customer_thread` (
   `id_customer_thread` int(11) unsigned NOT NULL auto_increment,
   `id_shop` INT(11) UNSIGNED NOT NULL DEFAULT '1',
diff --git a/install-dev/sql/upgrade/1.5.0.1.sql b/install-dev/sql/upgrade/1.5.0.1.sql
index d258f510d..de9d8b8df 100644
--- a/install-dev/sql/upgrade/1.5.0.1.sql
+++ b/install-dev/sql/upgrade/1.5.0.1.sql
@@ -97,6 +97,4 @@ CREATE TABLE `PREFIX_customer_message_sync_imap` (
   KEY `md5_header_index` (`md5_header`(4))
 ) ENGINE=ENGINE_TYPE DEFAULT CHARSET=utf8;
 
-CREATE INDEX `md5_header_index` ON `PREFIX_customer_message_sync_imap` (md5_header(4));
-
 ALTER TABLE  `PREFIX_customer_message` ADD  `private` TINYINT NOT NULL DEFAULT  '0' AFTER  `user_agent`;