diff --git a/libsolutil/BooleanLP.cpp b/libsolutil/BooleanLP.cpp
index d1cb0e524..c15efb129 100644
--- a/libsolutil/BooleanLP.cpp
+++ b/libsolutil/BooleanLP.cpp
@@ -58,9 +58,9 @@ void resizeAndSet(vector<T>& _vector, size_t _index, T _value)
 
 string toString(rational const& _x)
 {
-	if (_x == u256(1) << 256)
+	if (_x == bigint(1) << 256)
 		return "2**256";
-	else if (_x ==  (u256(1) << 256) - 1)
+	else if (_x == (bigint(1) << 256) - 1)
 		return "2**256-1";
 	else if (_x.denominator() == 1)
 		return _x.numerator().str();