diff --git a/partner_compassion/wizards/partner_merge_wizard.py b/partner_compassion/wizards/partner_merge_wizard.py
index d53b61e86..5d5bf5252 100644
--- a/partner_compassion/wizards/partner_merge_wizard.py
+++ b/partner_compassion/wizards/partner_merge_wizard.py
@@ -41,6 +41,13 @@ def action_merge(self):
                     "to send new labels to them."
                 )
             )
+        # check onboarding_new_donor_start_date for non-dst partner. If set,
+        # and dst partner is sponsor, clear the onboarding_new_donor_start_date.
+        if removing.onboarding_new_donor_start_date:
+            sponsor_category = self.env.ref("partner_compassion.res_partner_category_sponsor")
+            if sponsor_category in self.dst_partner_id.category_id:
+                removing.onboarding_new_donor_start_date = False
+
         old_emails = removing.filtered("email").mapped("email")
         new_email = self.dst_partner_id.email
         for email in old_emails: