diff --git a/plonky2/src/gates/selectors.rs b/plonky2/src/gates/selectors.rs
index 7c1b7277..36a3f536 100644
--- a/plonky2/src/gates/selectors.rs
+++ b/plonky2/src/gates/selectors.rs
@@ -187,9 +187,7 @@ pub(crate) fn selector_polynomials<F: RichField + Extendable<D>, const D: usize>
     let mut selector_vector: Vec<usize> = vec![usize::MAX; n];
     for (j, g) in instances.iter().enumerate() {
         let GateInstance { gate_ref, .. } = g;
-        let i = index(gate_ref.0.id());
-        let gr = group(i);
-        selector_vector[j] = i;
+        selector_vector[j] = index(gate_ref.0.id());
     }
 
     (
diff --git a/plonky2/src/plonk/circuit_data.rs b/plonky2/src/plonk/circuit_data.rs
index f3f6eeac..ce3fdb9b 100644
--- a/plonky2/src/plonk/circuit_data.rs
+++ b/plonky2/src/plonk/circuit_data.rs
@@ -46,7 +46,7 @@ use crate::plonk::circuit_builder::CircuitBuilder;
 use crate::plonk::config::{GenericConfig, Hasher};
 use crate::plonk::plonk_common::PlonkOracle;
 use crate::plonk::proof::{CompressedProofWithPublicInputs, ProofWithPublicInputs};
-use crate::plonk::prover::{prove,ProverOptions,default_prover_options};
+use crate::plonk::prover::{prove,prove_with_options,ProverOptions};
 use crate::plonk::verifier::verify;
 use crate::util::serialization::{
     Buffer, GateSerializer, IoResult, Read, WitnessGeneratorSerializer, Write,
@@ -196,12 +196,11 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
             &self.common,
             inputs,
             &mut TimingTree::default(),
-            &default_prover_options,
         )
     }
 
     pub fn prove_with_options(&self, inputs: PartialWitness<F>, opts: &ProverOptions) -> Result<ProofWithPublicInputs<F, C, D>> {
-        prove::<F, C, D>(
+        prove_with_options::<F, C, D>(
             &self.prover_only,
             &self.common,
             inputs,
@@ -305,12 +304,11 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
             &self.common,
             inputs,
             &mut TimingTree::default(),
-            &default_prover_options,
         )
     }
 
     pub fn prove_with_options(&self, inputs: PartialWitness<F>, opts: &ProverOptions) -> Result<ProofWithPublicInputs<F, C, D>> {
-        prove::<F, C, D>(
+        prove_with_options::<F, C, D>(
             &self.prover_only,
             &self.common,
             inputs,
diff --git a/plonky2/src/plonk/prover.rs b/plonky2/src/plonk/prover.rs
index adb7a38d..fa82d53b 100644
--- a/plonky2/src/plonk/prover.rs
+++ b/plonky2/src/plonk/prover.rs
@@ -122,7 +122,7 @@ pub struct ProverOptions {
     pub export_witness: Option<String>,      // export the full witness into the given file
 }
 
-pub const default_prover_options: ProverOptions = ProverOptions {
+pub const DEFAULT_PROVER_OPTIONS: ProverOptions = ProverOptions {
     export_witness: None,  
 };
 
@@ -154,6 +154,21 @@ pub fn prove<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D:
     common_data: &CommonCircuitData<F, D>,
     inputs: PartialWitness<F>,
     timing: &mut TimingTree,
+) -> Result<ProofWithPublicInputs<F, C, D>> {
+    prove_with_options(
+        prover_data,
+        common_data,
+        inputs,
+        timing,
+        &DEFAULT_PROVER_OPTIONS,
+    )
+}
+
+pub fn prove_with_options<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>(
+    prover_data: &ProverOnlyCircuitData<F, C, D>,
+    common_data: &CommonCircuitData<F, D>,
+    inputs: PartialWitness<F>,
+    timing: &mut TimingTree,
     prover_options: &ProverOptions,
 ) -> Result<ProofWithPublicInputs<F, C, D>>
 where
@@ -229,7 +244,7 @@ where
         None        => (),
         Some(fname) => {
             let things_to_export = collect_things_to_export::<F, C, D>( &common_data, &witness );
-            write_json_file(&fname, &things_to_export);
+            write_json_file(&fname, &things_to_export)?;
             println!("exported witness to `{}`",fname);
         },
     }