diff --git a/odoo/addons/base/models/ir_attachment.py b/odoo/addons/base/models/ir_attachment.py
index 11cbbc96871..5267a2f2166 100644
--- a/odoo/addons/base/models/ir_attachment.py
+++ b/odoo/addons/base/models/ir_attachment.py
@@ -412,7 +412,7 @@ class IrAttachment(models.Model):
     db_datas = fields.Binary('Database Data', attachment=False)
     store_fname = fields.Char('Stored Filename', index=True, unaccent=False)
     file_size = fields.Integer('File Size', readonly=True)
-    checksum = fields.Char("Checksum/SHA1", size=40, index=True, readonly=True)
+    checksum = fields.Char("Checksum/SHA1", size=40, readonly=True)
     mimetype = fields.Char('Mime Type', readonly=True)
     index_content = fields.Text('Indexed Content', readonly=True, prefetch=False)