# solving one variable with two equations

I cannot figure out why this gives and empty solution

```
x,y = var('x,y')
sol = solve([x+y == 2, y==x], x);sol
```

and this works properly

```
x,y = var('x,y')
sol = solve([x+y == 2, y==x], x,y);sol
```

Have I missed something?

Jakob