Restore 1.5 snapshot to 2.3 - mappings float <--> double issue

Elastic Stack Elasticsearch
1

I am trying to restore a snapshot from ES 1.5 to 2.3 but getting the following error. I did look at the breaking changes for mapping but could not figure why a field salary which was float before fails to restore with the following error

{
	"error": {
		"root_cause": [{
			"type": "snapshot_restore_exception",
			"reason": "[domain-restore-repo:es15-snapshot] cannot restore index [logs] because it cannot be upgraded"
		}],
		"type": "snapshot_restore_exception",
		"reason": "[domain-restore-repo:es15-snapshot] cannot restore index [logs] because it cannot be upgraded",
		"caused_by": {
			"type": "illegal_state_exception",
			"reason": "unable to upgrade the mappings for the index [logs], reason: [mapper [salary] cannot be changed from type [float] to [double]]",
			"caused_by": {
				"type": "illegal_argument_exception",
				"reason": "mapper [salary] cannot be changed from type [float] to [double]"
			}
		}
	},
	"status": 500
}
2

Any answers/suggestions on what the root cause could be and how to debug this further?