diff --git a/README.md b/README.md
index 878879a3..0c990e7a 100644
--- a/README.md
+++ b/README.md
@@ -269,6 +269,7 @@ Here are the Go packages that can be imported correctly:
 * [unicode/utf8](https://pkg.go.dev/unicode/utf8)
 * [unicode/utf16](https://pkg.go.dev/unicode/utf16)
 * [math](https://pkg.go.dev/math)
+* [math/big](https://pkg.go.dev/math/big) (partially)
 * [math/bits](https://pkg.go.dev/math/bits)
 * [math/cmplx](https://pkg.go.dev/math/cmplx)
 * [math/rand](https://pkg.go.dev/math/rand)
diff --git a/internal/lib/math/big/int.go b/internal/lib/math/big/int.go
index e970a174..f568938b 100644
--- a/internal/lib/math/big/int.go
+++ b/internal/lib/math/big/int.go
@@ -62,13 +62,16 @@ func (z *Int) SetInt64(x int64) *Int {
 		a.SetNegative(1)
 	} else {
 		a.SetWord(openssl.BN_ULONG(x))
+		a.SetNegative(0)
 	}
 	return z
 }
 
 // SetUint64 sets z to x and returns z.
 func (z *Int) SetUint64(x uint64) *Int {
-	(*openssl.BIGNUM)(z).SetWord(openssl.BN_ULONG(x))
+	a := (*openssl.BIGNUM)(z)
+	a.SetWord(openssl.BN_ULONG(x))
+	a.SetNegative(0)
 	return z
 }