Rhubarb Berry Custard Pie

Just made this with Grandma Gentle's summer blackberriers and our own rhubarb.
A little taste of summer in single digit temps.

1 1/2 c sugar
3/8 c flour
1/4 tsp salt
1 tsp vanilla
3 eggs
4 c rhubarb
4 c strawberries or other berry
double pie crust

Mix all ingredients.  Place in pie crust.  Bake 15 minutes at 425F.  Reduce oven to 375F, cover edges in foil, and bake another 75 minutes.