diff --git a/src/json.hpp b/src/json.hpp
index dafc1082..caeb079b 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -4824,6 +4826,7 @@ class binary_reader
 {
     using number_integer_t = typename BasicJsonType::number_integer_t;
     using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
+    using string_t = typename BasicJsonType::string_t;
 
   public:
     /*!
@@ -5607,9 +5611,9 @@ class binary_reader
     @throw parse_error.110 if input has less than @a len bytes
     */
     template<typename NumberType>
-    std::string get_string(const NumberType len)
+    string_t get_string(const NumberType len)
     {
-        std::string result;
+        string_t result;
         std::generate_n(std::back_inserter(result), len, [this]()
         {
             get();
@@ -5631,7 +5635,7 @@ class binary_reader
     @throw parse_error.110 if input ended
     @throw parse_error.113 if an unexpected byte is read
     */
-    std::string get_cbor_string()
+    string_t get_cbor_string()
     {
         check_eof();
 
@@ -5688,7 +5692,7 @@ class binary_reader
 
             case 0x7F: // UTF-8 string (indefinite length)
             {
-                std::string result;
+                string_t result;
                 while (get() != 0xFF)
                 {
                     check_eof();
@@ -5744,7 +5749,7 @@ class binary_reader
     @throw parse_error.110 if input ended
     @throw parse_error.113 if an unexpected byte is read
     */
-    std::string get_msgpack_string()
+    string_t get_msgpack_string()
     {
         check_eof();
 
@@ -6713,7 +6718,7 @@ class serializer
         return ((u <= 127) ? 0
                 : ((192 <= u and u <= 223) ? 1
                    : ((224 <= u and u <= 239) ? 2
-                      : ((240 <= u and u <= 247) ? 3 : std::string::npos))));
+                      : ((240 <= u and u <= 247) ? 3 : string_t::npos))));
     }
 
     /*!
@@ -6789,7 +6794,7 @@ class serializer
                     {
                         const auto bytes = bytes_following(static_cast<uint8_t>(s[i]));
                         // invalid characters will be detected by throw_if_invalid_utf8
-                        assert (bytes != std::string::npos);
+                        assert (bytes != string_t::npos);
 
                         if (bytes == 3)
                         {
@@ -6958,7 +6963,7 @@ class serializer
                     {
                         const auto bytes = bytes_following(static_cast<uint8_t>(s[i]));
                         // invalid characters will be detected by throw_if_invalid_utf8
-                        assert (bytes != std::string::npos);
+                        assert (bytes != string_t::npos);
 
                         // check that the additional bytes are present
                         assert(i + bytes < s.size());
@@ -7186,7 +7191,7 @@ class serializer
 
     @since version 3.0.0
     */
-    static void throw_if_invalid_utf8(const std::string& str)
+    static void throw_if_invalid_utf8(const string_t& str)
     {
         // start with state 0 (= accept)
         uint8_t state = 0;