diff --git a/sources/main.cpp b/sources/main.cpp
index 92980e7..07dc009 100644
--- a/sources/main.cpp
+++ b/sources/main.cpp
@@ -59,7 +59,7 @@ inline std::string getAddress(const Address& rawAddr) noexcept {
 inline std::string KeyToString(const unsigned char* key) noexcept {
     char result[65];
     const char* hexDigits = "0123456789abcdef";
-    for (size_t i = 0; i < 32; ++i) {
+    for (unsigned char i = 0; i < 32; i++) {
         result[2 * i] = hexDigits[key[i] >> 4];
         result[2 * i + 1] = hexDigits[key[i] & 0x0F];
     }