diff --git a/src/backends/plonky2/basetypes.rs b/src/backends/plonky2/basetypes.rs
index e8cda34..2436cb5 100644
--- a/src/backends/plonky2/basetypes.rs
+++ b/src/backends/plonky2/basetypes.rs
@@ -153,7 +153,7 @@ impl PartialOrd for Hash {
 impl fmt::Display for Hash {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let v0 = self.0[0].to_canonical_u64();
-        for i in 0..4 {
+        for i in 0..HASH_SIZE {
             write!(f, "{:02x}", (v0 >> (i * 8)) & 0xff)?;
         }
         write!(f, "…")
@@ -168,8 +168,8 @@ impl FromHex for Hash {
         // In little endian
         let bytes = <[u8; 32]>::from_hex(hex)?;
         let mut buf: [u8; 8] = [0; 8];
-        let mut inner = [F::ZERO; 4];
-        for i in 0..4 {
+        let mut inner = [F::ZERO; HASH_SIZE];
+        for i in 0..HASH_SIZE {
             buf.copy_from_slice(&bytes[8 * i..8 * (i + 1)]);
             inner[i] = F::from_canonical_u64(u64::from_le_bytes(buf));
         }
diff --git a/src/middleware/custom.rs b/src/middleware/custom.rs
index 5b34571..1c133cd 100644
--- a/src/middleware/custom.rs
+++ b/src/middleware/custom.rs
@@ -5,6 +5,7 @@ use std::{fmt, hash as h, iter::zip};
 use anyhow::{anyhow, Result};
 use plonky2::field::types::Field;
 
+use crate::backends::plonky2::basetypes::HASH_SIZE;
 use crate::util::hashmap_insert_no_dupe;
 
 use super::{
@@ -51,12 +52,13 @@ impl ToFields for HashOrWildcard {
         match self {
             HashOrWildcard::Hash(h) => h.to_fields(_params),
             HashOrWildcard::Wildcard(w) => {
-                let usizes: Vec<usize> = vec![0, 0, 0, *w];
+                let mut usizes: Vec<usize> = vec![0; HASH_SIZE - 1];
+                usizes.push(*w);
                 let fields: Vec<F> = usizes
                     .iter()
                     .map(|x| F::from_canonical_u64(*x as u64))
                     .collect();
-                (fields, 4)
+                (fields, HASH_SIZE)
             }
         }
     }
@@ -99,8 +101,7 @@ impl ToFields for StatementTmplArg {
         // Key(hash_or_wildcard1, hash_or_wildcard2)
         //    => (2, [hash_or_wildcard1], [hash_or_wildcard2])
         // In all three cases, we pad to 2 * hash_size + 1 = 9 field elements
-        let hash_size = 4;
-        let statement_tmpl_arg_size = 2 * hash_size + 1;
+        let statement_tmpl_arg_size = 2 * HASH_SIZE + 1;
         match self {
             StatementTmplArg::None => {
                 let fields: Vec<F> = std::iter::repeat_with(|| F::from_canonical_u64(0))
@@ -111,7 +112,7 @@ impl ToFields for StatementTmplArg {
             StatementTmplArg::Literal(v) => {
                 let fields: Vec<F> = std::iter::once(F::from_canonical_u64(1))
                     .chain(v.to_fields(_params).0)
-                    .chain(std::iter::repeat_with(|| F::from_canonical_u64(0)).take(hash_size))
+                    .chain(std::iter::repeat_with(|| F::from_canonical_u64(0)).take(HASH_SIZE))
                     .collect();
                 (fields, statement_tmpl_arg_size)
             }