Updating a lead using REST API which has duplicates (multiple leads with the same email address)

[Anonymous]

I am trying to update leads in Marketo, via REST API, and getting weird behavior. Here are my observations

1- Leads having duplicates (multiple leads with the same email address) are not getting updated. Also verified that NO new version of the contact is being created (with the data pushed via REST API).

2- Unique leads (no other lead exists with same email in the leads database) are updated without any issue.

3- If i merge duplicate leads (#1), merged lead is updated successfully via REST API.

My question is,

Is it expected behavior of Marketo? If so, how can i make the update (via REST API) working, without merging these duplicate leads?

[Steven_Vanderb3]

Have you examined the response JSON?  It should be denoting that the records aren't updating because multiple records match the lookup key (email address).  You need to specify a field in the dedupeBy parameter to denote which record you're attempting to update http://developers.marketo.com/rest-api/lead-database/#create_and_update