filterBy not distinguish positive and negative number

Considering this code

``` javascript
block in orderjson.Blocks | filterBy: ['ID_Block']: block_NM.ID_Block
```

if ID_Block have on array values [1, -1,3,5] and filter is set to 1.
I expect to print just first value, but filter print also -1 because comparision consider 1,-1 the same.

On the flipside of the coin, using only positive values it works fine (no duplicates).