diff --git a/redfish-core/ut/hex_utils_test.cpp b/redfish-core/ut/hex_utils_test.cpp
index 5084b8b..21387c6 100644
--- a/redfish-core/ut/hex_utils_test.cpp
+++ b/redfish-core/ut/hex_utils_test.cpp
@@ -31,7 +31,7 @@
 
 TEST(HexCharToNibble, chars)
 {
-    for (char c = 0; c < CHAR_MAX; ++c)
+    for (char c = 0; c < std::numeric_limits<char>::max(); ++c)
     {
         uint8_t expected = 16;
         if (isdigit(c) != 0)