Term does not return the exact results

I have the following nested schema: dataCollectorInfo.files.indexedData.objects.measures.properties.unit

"_source": {
	"dataCollectorInfo": {
		"files": {
			"indexedData": {
				"objects": {
					"measures": {
						"properties": {
							"unit": ...
						}
					}
				}
			}
		}
	}
}

i want to search for EXACT term with unit value = "Pa s". I tried the term query as bellow:

{
	"query": {
		"nested": {
			"path": "dataCollectorInfo.files.indexedData.objects.measures.properties",
			"query": {
				"bool": {
					"must": [
						{
							"term": {
								"dataCollectorInfo.files.indexedData.objects.measures.properties.unit.keyword": {
									"value": "Pa s"
								}
							}
						}
					]
				}
			}
		}
	}
}

For some reasons, even the results with unit value = "mPa s" are also returned.

Can some one tell me, what i have been missing ?