Issue with custom field type of numbers in Pipedrive API

Lately we experienced an issue with Pipedrive API and custom field type of numbers. While performing a search from the values of a specific field with only full exact matches against the given term /v1/itemSearch/field, the empty result was returned from Pipedrive API. The problem is that when we are trying to search for deal by custom field in a format 9999, but in Pipedrive it’s saved as 9999.0 with decimal separator.

Example of a result from API call:

   success: true,
   data: [ { id: 'deal_id', "custom_field_key": '9999.0' } ],
   additional_data: { start: 0, limit: 100, more_items_in_collection: false },

Even thought in Pipedrive interface the custom field value looks as expected 9999. How this could be explained?

Thank you.