diff --git a/include/bigint.h b/include/bigint.h
index 85b2ac8..11b637f 100644
--- a/include/bigint.h
+++ b/include/bigint.h
@@ -88,7 +88,7 @@ namespace boost
   {
     inline void to_json(nlohmann::json& j, const uint256_t& v)
     {
-      j = to_hex_str(v);
+      j = to_lower_hex_str(v);
     }
 
     inline void from_json(const nlohmann::json& j, uint256_t& v)
diff --git a/include/util.h b/include/util.h
index 12ae34e..adcde12 100644
--- a/include/util.h
+++ b/include/util.h
@@ -101,9 +101,6 @@ namespace evm
     // Start at index 2 to skip the "0x" prefix
     const auto h = keccak_256(s, 2);
 
-    std::cout << s << std::endl;
-    std::cout << to_hex_string(h) << std::endl;
-
     for (size_t i = 0; i < s.size() - 2; ++i)
     {
       auto& c = s[i + 2];