- Operating System: macOS High Sierra
- brms Version: 2.6.0

Say I have a model with two predictors and an intercept. E.g.,

```
fit1 <-
brm(data = my_data,
family = gaussian,
y ~ 1 + x1 + x2)
```

I’d like to constrain the model such that the sum of `x1`

and `x2`

equals 0. What would the syntax for such a constraint be?