Merging Contacts in Salesforce removes Converted Lead data in Marketo

[KerryMcClauss]

Hi all,

Hope someone can help me understand if this is expected behavior or not.  Here is the scenario:

• Lead comes through Marketo form and is synced to Salesforce.
• Sales works lead and SQL Date field is populated in Salesforce and syncs to marketo. SQL Date is a lead field only. It is not mapped to Contact.
• Lead is converted to Contact.
• At some point a duplicate contact is created and these two contacts are merged.
• Upon merge, it seems that the SQL Date field is nulled out in Marketo.  Though there is no record of this in the Marketo Activity History.  The Lead in Salesforce still has the correct Converted Contact Id. 
• Contact that don't get merged will still have the SQL Date from the converted lead populated in Marketo. 

Why does merging contacts wipe out the converted lead data?  I don't want to have to map every lead field to contacts. Is there any other way to address this?

[SanfordWhiteman]

This is expected behavior.

A field isn’t expected to survive a Contact → Contact merge if it’s not mapped from the Contact. If you want to have persistent fields, they need to either be mapped in Marketo or copied in SFDC.