Blackberry Cranberry Sauce

I got this recipe from Baking Bites and made it for Thanksgiving this year, though I left out the allspice lest my very traditional family mutiny. I liked it a lot, but maybe added too much water at the beginning, as it stayed fairly watery.

Blackberry Cranberry Sauce
12-oz bag cranberries
2 cups blackberries (approx 12-oz)
1 cup sugar
1/4 tsp salt
[1/4 tsp ground allspice...I omitted]

Place cranberries in a medium saucepan and fill about 1-inch deep with water. Cook over medium-high heat until cranberries start to pop. Cook for 1-2 minutes, until popping slows. Add in blackberries, sugar, salt and allspice. Stir well and cook over medium heat until sauce comes just to a simmer and starts to thicken.
Use a potato masher to gently crush the berries, the cook for an additional minute.
Pour sauce out into a heat resistant dish, cover and let cool to room temperature. Refrigerate until ready to serve.
Berries will keep, refrigerated, for at least a week.

Makes about 4 cups