diff --git a/sale_automatic_workflow/models/account_invoice.py b/sale_automatic_workflow/models/account_invoice.py
index e822facbebbf..8be06fda4b99 100644
--- a/sale_automatic_workflow/models/account_invoice.py
+++ b/sale_automatic_workflow/models/account_invoice.py
@@ -13,3 +13,10 @@ class AccountInvoice(models.Model):
         comodel_name='sale.workflow.process',
         string='Sale Workflow Process'
     )
+
+    @api.multi
+    def action_cancel(self):
+        for inv in self:
+            if inv.workflow_process_id:
+                inv.workflow_process_id = None
+        return super(AccountInvoice, self).action_cancel()