diff --git a/plonky2/src/fri/oracle.rs b/plonky2/src/fri/oracle.rs
index efe34939..75f8847a 100644
--- a/plonky2/src/fri/oracle.rs
+++ b/plonky2/src/fri/oracle.rs
@@ -185,6 +185,8 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
         // where `alpha` is a random challenge in the extension field.
         // The final polynomial is then computed as `final_poly = sum_i alpha^(k_i) (F_i(X) - F_i(z_i))/(X-z_i)`
         // where the `k_i`s are chosen such that each power of `alpha` appears only once in the final sum.
+        // There are usually two batches for the openings at `zeta` and `g * zeta`.
+        // The oracles used in Plonky2 are given in `FRI_ORACLES` in `plonky2/src/plonk/plonk_common.rs`.
         for FriBatchInfo { point, polynomials } in &instance.batches {
             // Collect the coefficients of all the polynomials in `polynomials`.
             let polys_coeff = polynomials.iter().map(|fri_poly| {