diff --git a/src/gadgets/arithmetic_u32.rs b/src/gadgets/arithmetic_u32.rs
index 0d88d52c..7cb5b7c5 100644
--- a/src/gadgets/arithmetic_u32.rs
+++ b/src/gadgets/arithmetic_u32.rs
@@ -36,6 +36,12 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         self.assert_zero(x.0)
     }
 
+    fn get_u32_target(&self, target: U32Target) -> F {
+        let result = self.get_target(target.0);
+        debug_assert!(result.to_canonical_u64() < 1 << 32u64);
+        result
+    }
+
     // Returns x * y + z.
     pub fn mul_add_u32(
         &mut self,
diff --git a/src/gadgets/biguint.rs b/src/gadgets/biguint.rs
index b30b4680..54589f54 100644
--- a/src/gadgets/biguint.rs
+++ b/src/gadgets/biguint.rs
@@ -41,7 +41,22 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         }
     }
 
-    fn pad_biguints(&mut self, a: BigUintTarget, b: BigUintTarget) -> (BigUintTarget, BigUintTarget) {
+    fn get_biguint_target(&self, target: BigUintTarget) -> BigUint {
+        let mut result = BigUint::zero();
+        let base = BigUint::from_u64(1 << 32u64);
+        for &limb in target.limbs.iter().rev() {
+            let limb_value = self.get_target(limb.0);
+            result += BigUint::from_u64(limb_value.to_canonical_u64());
+            result *= base;
+        }
+        result
+    }
+
+    fn pad_biguints(
+        &mut self,
+        a: BigUintTarget,
+        b: BigUintTarget,
+    ) -> (BigUintTarget, BigUintTarget) {
         if a.num_limbs() > b.num_limbs() {
             let mut padded_b_limbs = b.limbs.clone();
             padded_b_limbs.extend(self.add_virtual_u32_targets(a.num_limbs() - b.num_limbs()));
@@ -69,11 +84,11 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
     }
 
     fn add_virtual_biguint_target(&mut self, num_limbs: usize) -> BigUintTarget {
-        let limbs = (0..num_limbs).map(|_| self.add_virtual_u32_target()).collect();
+        let limbs = (0..num_limbs)
+            .map(|_| self.add_virtual_u32_target())
+            .collect();
 
-        BigUintTarget {
-            limbs,
-        }
+        BigUintTarget { limbs }
     }
 
     // Add two `BigUintTarget`s.
@@ -144,7 +159,11 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         }
     }
 
-    pub fn div_rem_biguint(&mut self, a: BigUintTarget, b: BigUintTarget) -> (BigUintTarget, BigUintTarget) {
+    pub fn div_rem_biguint(
+        &mut self,
+        a: BigUintTarget,
+        b: BigUintTarget,
+    ) -> (BigUintTarget, BigUintTarget) {
         let num_limbs = a.limbs.len();
         let div = self.add_virtual_biguint_target(num_limbs);
         let rem = self.add_virtual_biguint_target(num_limbs);
@@ -159,11 +178,10 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
 
         let div_b = self.mul_biguint(div, b);
         let div_b_plus_rem = self.add_biguint(div_b, rem);
-        self.connect_biguint(x, div_b_plus_rem);
+        self.connect_biguint(a, div_b_plus_rem);
 
-        let 
-
-        self.assert_one()
+        let cmp_rem_b = self.cmp_biguint(rem, b);
+        self.assert_one(cmp_rem_b.target);
 
         (div, rem)
     }
@@ -182,10 +200,13 @@ impl<F: RichField + Extendable<D>, const D: usize> SimpleGenerator<F>
     for BigUintDivRemGenerator<F, D>
 {
     fn dependencies(&self) -> Vec<Target> {
-        self.a.limbs.iter().map(|&l| l.0).chain(self.b.limbs.iter().map(|&l| l.0)).collect()
+        self.a
+            .limbs
+            .iter()
+            .map(|&l| l.0)
+            .chain(self.b.limbs.iter().map(|&l| l.0))
+            .collect()
     }
 
-    fn run_once(&self, witness: &PartitionWitness<F>, out_buffer: &mut GeneratedValues<F>) {
-        
-    }
-}
\ No newline at end of file
+    fn run_once(&self, witness: &PartitionWitness<F>, out_buffer: &mut GeneratedValues<F>) {}
+}
diff --git a/src/iop/witness.rs b/src/iop/witness.rs
index 12186fb1..13a374e2 100644
--- a/src/iop/witness.rs
+++ b/src/iop/witness.rs
@@ -1,7 +1,7 @@
 use std::collections::HashMap;
 use std::convert::TryInto;
 
-use num::BigUint;
+use num::{BigUint, FromPrimitive, Zero};
 
 use crate::field::extension_field::target::ExtensionTarget;
 use crate::field::extension_field::{Extendable, FieldExtension};
@@ -57,24 +57,12 @@ pub trait Witness<F: Field> {
         panic!("not a bool")
     }
 
-    fn get_u32_target(&self, target: U32Target) -> F {
-        let result = self.get_target(target.0);
-        debug_assert!(result.to_canonical_u64() < 1 << 32u64);
-        result
-    }
-
     fn get_hash_target(&self, ht: HashOutTarget) -> HashOut<F> {
         HashOut {
             elements: self.get_targets(&ht.elements).try_into().unwrap(),
         }
     }
 
-    fn get_biguint_target(&self, target: BigUintTarget) -> BigUint {
-        let mut result = BigUint::zero();
-        for (i, &limb) in target
-        result
-    }
-
     fn get_wire(&self, wire: Wire) -> F {
         self.get_target(Target::Wire(wire))
     }