diff --git a/evm/src/cpu/gas.rs b/evm/src/cpu/gas.rs
index ae923fde6b..694fb0f47e 100644
--- a/evm/src/cpu/gas.rs
+++ b/evm/src/cpu/gas.rs
@@ -70,6 +70,10 @@ fn eval_packed_accumulate<P: PackedField>(
         })
         .sum();
 
+    // TODO: This may cause soundness issue if the recomputed gas (as u64) overflows the field size.
+    // This is fine as we are only using two-limbs for testing purposes (to support all cases from
+    // the Ethereum test suite).
+    // This should be changed back to a single 32-bit limb before going into production!
     let gas_diff = nv.gas[1] * P::Scalar::from_canonical_u64(1 << 32) + nv.gas[0]
         - (lv.gas[1] * P::Scalar::from_canonical_u64(1 << 32) + lv.gas[0]);
     let constr = gas_diff - gas_used;
@@ -157,6 +161,10 @@ fn eval_ext_circuit_accumulate<F: RichField + Extendable<D>, const D: usize>(
         },
     );
 
+    // TODO: This may cause soundness issue if the recomputed gas (as u64) overflows the field size.
+    // This is fine as we are only using two-limbs for testing purposes (to support all cases from
+    // the Ethereum test suite).
+    // This should be changed back to a single 32-bit limb before going into production!
     let nv_gas =
         builder.mul_const_add_extension(F::from_canonical_u64(1 << 32), nv.gas[1], nv.gas[0]);
     let lv_gas =
diff --git a/evm/src/proof.rs b/evm/src/proof.rs
index d63ddc8914..fd6c4f3e9a 100644
--- a/evm/src/proof.rs
+++ b/evm/src/proof.rs
@@ -89,6 +89,10 @@ pub struct BlockHashes {
     pub cur_hash: H256,
 }
 
+// TODO: Before going into production, `block_gas_used` and `block_gaslimit` here
+// as well as `gas_used_before` / `gas_used_after` in `ExtraBlockData` should be
+// updated to fit in a single 32-bit limb, as supporting 64-bit values for those
+// fields is only necessary for testing purposes.
 /// Metadata contained in a block header. Those are identical between
 /// all state transition proofs within the same block.
 #[derive(Debug, Clone, Default, Deserialize, Serialize)]