diff --git a/big/int.go b/big/int.go
index 4b9cdb80..67302edb 100644
--- a/big/int.go
+++ b/big/int.go
@@ -12,6 +12,8 @@ import (
 // BigIntMaxSerializedLen is the max length of a byte slice representing a CBOR serialized big.
 const BigIntMaxSerializedLen = 128
 
+var zeroInternal = big.NewInt(0)
+
 type Int struct {
 	*big.Int
 }
@@ -71,19 +73,19 @@ func Product(ints ...Int) Int {
 }
 
 func Mul(a, b Int) Int {
-	return Int{big.NewInt(0).Mul(a.Int, b.Int)}
+	return Int{big.NewInt(0).Mul(a.i(), b.i())}
 }
 
 func Div(a, b Int) Int {
-	return Int{big.NewInt(0).Div(a.Int, b.Int)}
+	return Int{big.NewInt(0).Div(a.i(), b.i())}
 }
 
 func Mod(a, b Int) Int {
-	return Int{big.NewInt(0).Mod(a.Int, b.Int)}
+	return Int{big.NewInt(0).Mod(a.i(), b.i())}
 }
 
 func Add(a, b Int) Int {
-	return Int{big.NewInt(0).Add(a.Int, b.Int)}
+	return Int{big.NewInt(0).Add(a.i(), b.i())}
 }
 
 func Sum(ints ...Int) Int {
@@ -103,32 +105,32 @@ func Subtract(num1 Int, ints ...Int) Int {
 }
 
 func Sub(a, b Int) Int {
-	return Int{big.NewInt(0).Sub(a.Int, b.Int)}
+	return Int{big.NewInt(0).Sub(a.i(), b.i())}
 }
 
 // Returns a**e unless e <= 0 (in which case returns 1).
 func Exp(a Int, e Int) Int {
-	return Int{big.NewInt(0).Exp(a.Int, e.Int, nil)}
+	return Int{big.NewInt(0).Exp(a.i(), e.i(), nil)}
 }
 
 // Returns x << n
 func Lsh(a Int, n uint) Int {
-	return Int{big.NewInt(0).Lsh(a.Int, n)}
+	return Int{big.NewInt(0).Lsh(a.i(), n)}
 }
 
 // Returns x >> n
 func Rsh(a Int, n uint) Int {
-	return Int{big.NewInt(0).Rsh(a.Int, n)}
+	return Int{big.NewInt(0).Rsh(a.i(), n)}
 }
 
 func BitLen(a Int) uint {
-	return uint(a.Int.BitLen())
+	return uint(a.i().BitLen())
 }
 
 func Max(x, y Int) Int {
 	// taken from max.Max()
 	if x.Equals(Zero()) && x.Equals(y) {
-		if x.Sign() != 0 {
+		if x.i().Sign() != 0 {
 			return y
 		}
 		return x
@@ -142,7 +144,7 @@ func Max(x, y Int) Int {
 func Min(x, y Int) Int {
 	// taken from max.Min()
 	if x.Equals(Zero()) && x.Equals(y) {
-		if x.Sign() != 0 {
+		if x.i().Sign() != 0 {
 			return x
 		}
 		return y
@@ -154,7 +156,14 @@ func Min(x, y Int) Int {
 }
 
 func Cmp(a, b Int) int {
-	return a.Int.Cmp(b.Int)
+	return a.i().Cmp(b.i())
+}
+
+func (bi Int) i() *big.Int {
+	if bi.Int != nil {
+		return bi.Int
+	}
+	return zeroInternal
 }
 
 // LessThan returns true if bi < o
@@ -179,7 +188,7 @@ func (bi Int) GreaterThanEqual(o Int) bool {
 
 // Neg returns the negative of bi.
 func (bi Int) Neg() Int {
-	return Int{big.NewInt(0).Neg(bi.Int)}
+	return Int{big.NewInt(0).Neg(bi.i())}
 }
 
 // Abs returns the absolute value of bi.
@@ -338,7 +347,7 @@ func (bi *Int) UnmarshalCBOR(br io.Reader) error {
 }
 
 func (bi *Int) IsZero() bool {
-	return bi.Int.Sign() == 0
+	return bi.NilOrZero()
 }
 
 func (bi *Int) Nil() bool {