Migrate D2D UI - Source field missing from dropdown menu when editing field mappings I got an PDOException: SQLSTATE[HY000]: General error: 1366 Incorrect integer value error on one of the fields for a content type that I'm importing from a D6 site to a D7 site, and the import of all those nodes is failing. I looked at the field on the Field Mappings page, and found that the field is not in the Source dropdown menu, and therefore cannot be mapped. I think this is why the import is failing. The field exists in both the source D6 database and the destination D7 database.

How do I get Migrate D2D to recognize this field so that it appears in the field mappings menu?
I found the cause of the problem, and a solution:

I had cloned my old D6 site, then performed the core and CCK upgrade to D7 as described in Drupal's documentation, during which I mistakenly converted the above-mentioned field to a Boolean type when it should have been (based on the old site's field) converted to the List (text) type. I manually deleted the field and recreated it as the proper type, ran the migration, and the nodes were imported as expected.