diff --git a/include/fkYAML/detail/input/lexical_analyzer.hpp b/include/fkYAML/detail/input/lexical_analyzer.hpp
index 709e33f9..39e016b2 100644
--- a/include/fkYAML/detail/input/lexical_analyzer.hpp
+++ b/include/fkYAML/detail/input/lexical_analyzer.hpp
@@ -153,7 +153,7 @@ class lexical_analyzer
                     m_input_handler.get_next();
                     break;
                 }
-                m_value_buffer.push_back(next);
+                m_value_buffer.push_back(char_traits_type::to_char_type(next));
             }
             return m_last_token_type = lexical_token_t::ANCHOR_PREFIX;
         }
@@ -171,7 +171,7 @@ class lexical_analyzer
                     m_input_handler.get_next();
                     break;
                 }
-                m_value_buffer.push_back(next);
+                m_value_buffer.push_back(char_traits_type::to_char_type(next));
             }
             return m_last_token_type = lexical_token_t::ALIAS_PREFIX;
         }
@@ -212,7 +212,7 @@ class lexical_analyzer
         case '\'':
             return m_last_token_type = scan_string();
         case '~':
-            m_value_buffer = current;
+            m_value_buffer = char_traits_type::to_char_type(current);
             return m_last_token_type = lexical_token_t::NULL_VALUE;
         case '+':
             return m_last_token_type = scan_number();
@@ -495,19 +495,19 @@ class lexical_analyzer
         {
             throw fkyaml::exception("Invalid YAML major version found.");
         }
-        m_value_buffer.push_back(m_input_handler.get_current());
+        m_value_buffer.push_back(char_traits_type::to_char_type(m_input_handler.get_current()));
 
         if (m_input_handler.get_next() != '.')
         {
             throw fkyaml::exception("A period must be followed after the YAML major version.");
         }
-        m_value_buffer.push_back(m_input_handler.get_current());
+        m_value_buffer.push_back(char_traits_type::to_char_type(m_input_handler.get_current()));
 
         switch (m_input_handler.get_next())
         {
         case '1':
         case '2':
-            m_value_buffer.push_back(m_input_handler.get_current());
+            m_value_buffer.push_back(char_traits_type::to_char_type(m_input_handler.get_current()));
             break;
         case '0':
         case '3':
@@ -548,14 +548,14 @@ class lexical_analyzer
         switch (current)
         {
         case '-':
-            m_value_buffer.push_back(current);
+            m_value_buffer.push_back(char_traits_type::to_char_type(current));
             ret = scan_negative_number();
             break;
         case '+':
             ret = scan_decimal_number();
             break;
         case '0':
-            m_value_buffer.push_back(current);
+            m_value_buffer.push_back(char_traits_type::to_char_type(current));
             ret = scan_number_after_zero_at_first();
             break;
         case '1':
@@ -567,7 +567,7 @@ class lexical_analyzer
         case '7':
         case '8':
         case '9':
-            m_value_buffer.push_back(current);
+            m_value_buffer.push_back(char_traits_type::to_char_type(current));
             ret = scan_decimal_number();
             break;
         default:                                                                   // LCOV_EXCL_LINE
@@ -601,7 +601,7 @@ class lexical_analyzer
 
         if (std::isdigit(next))
         {
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             return scan_decimal_number();
         }
 
@@ -634,7 +634,7 @@ class lexical_analyzer
         switch (next)
         {
         case '.':
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             return scan_decimal_number_after_decimal_point();
         case 'o':
             // Do not store 'o' since std::strtoull does not support "0o" but "0" as the prefix for octal numbers.
@@ -642,7 +642,7 @@ class lexical_analyzer
             // See "10.3.2. Tag Resolution" section in https://yaml.org/spec/1.2.2/
             return scan_octal_number();
         case 'x':
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             return scan_hexadecimal_number();
         default:
             return lexical_token_t::INTEGER_VALUE;
@@ -660,7 +660,7 @@ class lexical_analyzer
 
         if (std::isdigit(next))
         {
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             scan_decimal_number();
             return lexical_token_t::FLOAT_NUMBER_VALUE;
         }
@@ -678,12 +678,12 @@ class lexical_analyzer
         char_int_type next = m_input_handler.get_next();
         if (next == '+' || next == '-')
         {
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             scan_decimal_number_after_sign();
         }
         else if (std::isdigit(next))
         {
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             scan_decimal_number();
         }
         else
@@ -704,7 +704,7 @@ class lexical_analyzer
 
         if (std::isdigit(next))
         {
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             return scan_decimal_number();
         }
 
@@ -722,24 +722,25 @@ class lexical_analyzer
 
         if (std::isdigit(next))
         {
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             return scan_decimal_number();
         }
 
         if (next == '.')
         {
-            if (m_value_buffer.find(next) != string_type::npos) // NOLINT(abseil-string-find-str-contains)
+            // NOLINTNEXTLINE(abseil-string-find-str-contains)
+            if (m_value_buffer.find(char_traits_type::to_char_type(next)) != string_type::npos)
             {
                 // TODO: support this use case (e.g. version info like 1.0.0)
                 throw fkyaml::exception("Multiple decimal points found in a token.");
             }
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             return scan_decimal_number_after_decimal_point();
         }
 
         if (next == 'e' || next == 'E')
         {
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             return scan_decimal_number_after_exponent();
         }
 
@@ -756,7 +757,7 @@ class lexical_analyzer
         char_int_type next = m_input_handler.get_next();
         if ('0' <= next && next <= '7')
         {
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             scan_octal_number();
         }
         return lexical_token_t::INTEGER_VALUE;
@@ -772,7 +773,7 @@ class lexical_analyzer
         char_int_type next = m_input_handler.get_next();
         if (std::isxdigit(next))
         {
-            m_value_buffer.push_back(next);
+            m_value_buffer.push_back(char_traits_type::to_char_type(next));
             scan_hexadecimal_number();
         }
         return lexical_token_t::INTEGER_VALUE;
@@ -818,7 +819,7 @@ class lexical_analyzer
                 {
                     return lexical_token_t::STRING_VALUE;
                 }
-                m_value_buffer.push_back(current);
+                m_value_buffer.push_back(char_traits_type::to_char_type(current));
                 continue;
             }
 
@@ -836,7 +837,7 @@ class lexical_analyzer
                 }
 
                 // if the target is a single-quoted string token.
-                m_value_buffer.push_back(current);
+                m_value_buffer.push_back(char_traits_type::to_char_type(current));
                 continue;
             }
 
@@ -852,7 +853,7 @@ class lexical_analyzer
                 // an escaped single quotation mark.
                 if (m_input_handler.test_next_char('\''))
                 {
-                    m_value_buffer.push_back(m_input_handler.get_next());
+                    m_value_buffer.push_back(char_traits_type::to_char_type(m_input_handler.get_next()));
                     continue;
                 }
 
@@ -865,7 +866,7 @@ class lexical_analyzer
                 // Just regard a colon as a character if surrounded by quotation marks.
                 if (needs_last_double_quote || needs_last_single_quote)
                 {
-                    m_value_buffer.push_back(current);
+                    m_value_buffer.push_back(char_traits_type::to_char_type(current));
                     continue;
                 }
 
@@ -875,7 +876,7 @@ class lexical_analyzer
                 // A colon as a key separator must be followed by a space or a newline code.
                 if (next != ' ' && next != '\r' && next != '\n')
                 {
-                    m_value_buffer.push_back(current);
+                    m_value_buffer.push_back(char_traits_type::to_char_type(current));
                     continue;
                 }
 
@@ -895,7 +896,7 @@ class lexical_analyzer
                 // Just regard a comma as a character if surrounded by quotation marks.
                 if (needs_last_double_quote || needs_last_single_quote)
                 {
-                    m_value_buffer.push_back(current);
+                    m_value_buffer.push_back(char_traits_type::to_char_type(current));
                     continue;
                 }
 
@@ -908,7 +909,7 @@ class lexical_analyzer
                 // just regard a right square bracket as a character if surrounded by quotation marks.
                 if (needs_last_double_quote || needs_last_single_quote)
                 {
-                    m_value_buffer.push_back(current);
+                    m_value_buffer.push_back(char_traits_type::to_char_type(current));
                     continue;
                 }
 
@@ -921,7 +922,7 @@ class lexical_analyzer
                 // just regard a right curly brace as a character if surrounded by quotation marks.
                 if (needs_last_double_quote || needs_last_single_quote)
                 {
-                    m_value_buffer.push_back(current);
+                    m_value_buffer.push_back(char_traits_type::to_char_type(current));
                     continue;
                 }
 
@@ -1018,7 +1019,7 @@ class lexical_analyzer
             // Handle ASCII characters except control characters.
             if (current <= 0x7E)
             {
-                m_value_buffer.push_back(current);
+                m_value_buffer.push_back(char_traits_type::to_char_type(current));
                 continue;
             }
 
@@ -1056,7 +1057,7 @@ class lexical_analyzer
         case 0x08:
             throw fkyaml::exception("Control character U+0008 (BS) must be escaped to \\b or \\u0008.");
         case 0x09: // HT
-            m_value_buffer.push_back(c);
+            m_value_buffer.push_back(char_traits_type::to_char_type(c));
             break;
         // 0x0A(LF) has already been handled above.
         case 0x0B: