diff --git a/htdocs/core/class/extrafields.class.php b/htdocs/core/class/extrafields.class.php
index 4cfb2fed5db..9b1f5921740 100644
--- a/htdocs/core/class/extrafields.class.php
+++ b/htdocs/core/class/extrafields.class.php
@@ -749,7 +749,7 @@ class ExtraFields
 						$sql = "ALTER TABLE ".$this->db->prefix().$table." ADD UNIQUE INDEX uk_".$table."_".$this->db->sanitize($attrname)." (".$this->db->sanitize($attrname).")";
 					} else {
 						dol_syslog(get_class($this).'::update_common', LOG_DEBUG);
-						$sql = "ALTER TABLE ".$this->db->prefix().$table." DROP INDEX IF EXISTS uk_".$table."_".$this->db->sanitize($attrname);
+						$sql = "ALTER TABLE ".$this->db->prefix().$table." DROP INDEX uk_".$table."_".$this->db->sanitize($attrname);
 					}
 					dol_syslog(get_class($this).'::update', LOG_DEBUG);
 					$resql = $this->db->query($sql, 1, 'dml');