diff --git a/plonky2/src/plonk/circuit_builder.rs b/plonky2/src/plonk/circuit_builder.rs
index d045aa6e..8e2f2e10 100644
--- a/plonky2/src/plonk/circuit_builder.rs
+++ b/plonky2/src/plonk/circuit_builder.rs
@@ -639,6 +639,7 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         let mut timing = TimingTree::new("preprocess", Level::Trace);
         let start = Instant::now();
         let rate_bits = self.config.fri_config.rate_bits;
+        let cap_height = self.config.fri_config.cap_height;
 
         // Hash the public inputs, and route them to a `PublicInputGate` which will enforce that
         // those hash wires match the claimed public inputs.
@@ -664,7 +665,7 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         let degree_bits = log2_strict(degree);
         let fri_params = self.fri_params(degree_bits);
         assert!(
-            fri_params.total_arities() <= degree_bits - self.config.fri_config.cap_height,
+            fri_params.total_arities() <= degree_bits + rate_bits - cap_height,
             "FRI total reduction arity is too large.",
         );
 
@@ -705,7 +706,7 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
             constants_sigmas_vecs,
             rate_bits,
             PlonkOracle::CONSTANTS_SIGMAS.blinding,
-            self.config.fri_config.cap_height,
+            cap_height,
             &mut timing,
             Some(&fft_root_table),
         );
diff --git a/starky/src/prover.rs b/starky/src/prover.rs
index 4fef0b4a..be1f198b 100644
--- a/starky/src/prover.rs
+++ b/starky/src/prover.rs
@@ -41,8 +41,10 @@ where
     let degree = trace.len();
     let degree_bits = log2_strict(degree);
     let fri_params = config.fri_params(degree_bits);
+    let rate_bits = config.fri_config.rate_bits;
+    let cap_height = config.fri_config.cap_height;
     assert!(
-        fri_params.total_arities() <= degree_bits - config.fri_config.cap_height,
+        fri_params.total_arities() <= degree_bits + rate_bits - cap_height,
         "FRI total reduction arity is too large.",
     );
 
@@ -58,8 +60,6 @@ where
             .collect()
     );
 
-    let rate_bits = config.fri_config.rate_bits;
-    let cap_height = config.fri_config.cap_height;
     let trace_commitment = timed!(
         timing,
         "compute trace commitment",