diff --git a/plonky2/src/plonk/config.rs b/plonky2/src/plonk/config.rs
index 36d29cff..cacc8421 100644
--- a/plonky2/src/plonk/config.rs
+++ b/plonky2/src/plonk/config.rs
@@ -53,7 +53,7 @@ pub trait Hasher<F: RichField>: Sized + Clone + Debug + Eq + PartialEq {
     /// Hash the slice if necessary to reduce its length to ~256 bits. If it already fits, this is a
     /// no-op.
     fn hash_or_noop(inputs: &[F]) -> Self::Hash {
-        if inputs.len() <= 4 {
+        if inputs.len() * 8 <= Self::HASH_SIZE {
             let mut inputs_bytes = vec![0u8; Self::HASH_SIZE];
             for i in 0..inputs.len() {
                 inputs_bytes[i * 8..(i + 1) * 8]