diff --git a/src/math/bigfix/u256.h b/src/math/bigfix/u256.h
index 91bbd9742..7d6e11991 100644
--- a/src/math/bigfix/u256.h
+++ b/src/math/bigfix/u256.h
@@ -6,6 +6,10 @@ class u256 {
     uint64_t m_num[4];
 public:
     u256() { memset(this, 0, sizeof(*this)); }
+    u256(uint64_t n);
     u256(uint64_t const* v) { memcpy(m_num, v, sizeof(*this)); }
     u256 operator*(u256 const& other) const;
+    u256 operator+(u256 const& other) const;
+    u256 operator-(u256 const& other) const;
+    
 };