diff --git a/docs/mkdocs/docs/api/basic_json/to_msgpack.md b/docs/mkdocs/docs/api/basic_json/to_msgpack.md
index 0330461ea..b3bcaab7f 100644
--- a/docs/mkdocs/docs/api/basic_json/to_msgpack.md
+++ b/docs/mkdocs/docs/api/basic_json/to_msgpack.md
@@ -30,6 +30,10 @@ The exact mapping and its limitations are described on a [dedicated page](../../
 1. MessagePack serialization as a byte vector
 2. (none)
 
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
+
 ## Exceptions
 
 - Throws [`out_of_range.412`](../../home/exceptions.md#jsonexceptionout_of_range412) if the length of a string, binary
@@ -39,10 +43,6 @@ The exact mapping and its limitations are described on a [dedicated page](../../
   exceeds 255, the maximum of the MessagePack ext type; example:
   `"subtype 70000 is too large for the MessagePack ext type (max 255)"`
 
-## Exception safety
-
-Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
-
 ## Complexity
 
 Linear in the size of the JSON value `j`.
diff --git a/include/nlohmann/detail/output/binary_writer.hpp b/include/nlohmann/detail/output/binary_writer.hpp
index 9d2ed55d7..a874855fe 100644
--- a/include/nlohmann/detail/output/binary_writer.hpp
+++ b/include/nlohmann/detail/output/binary_writer.hpp
@@ -479,6 +479,7 @@ class binary_writer
             JSON_THROW(out_of_range::create(412, concat("MessagePack length ", std::to_string(length), " exceeds maximum of ", std::to_string((std::numeric_limits<std::uint32_t>::max)())), &j));
         }
 
+        static_cast<void>(j);
         return static_cast<std::uint32_t>(length);
     }
 
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index cd523127e..2ab9fb027 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -19944,6 +19944,7 @@ class binary_writer
             JSON_THROW(out_of_range::create(412, concat("MessagePack length ", std::to_string(length), " exceeds maximum of ", std::to_string((std::numeric_limits<std::uint32_t>::max)())), &j));
         }
 
+        static_cast<void>(j);
         return static_cast<std::uint32_t>(length);
     }
 
diff --git a/tests/src/unit-msgpack.cpp b/tests/src/unit-msgpack.cpp
index c1693065b..0c0aee8bc 100644
--- a/tests/src/unit-msgpack.cpp
+++ b/tests/src/unit-msgpack.cpp
@@ -2208,7 +2208,10 @@ TEST_CASE("MessagePack lengths beyond UINT32_MAX cannot be serialized")
         const beyond_uint32_binary_json ext = beyond_uint32_binary_json::binary(beyond_uint32_binary_t{}, 42);
         CHECK_THROWS_WITH_AS(beyond_uint32_binary_json::to_msgpack(ext), expected, beyond_uint32_binary_json::out_of_range&);
 
-        const beyond_uint32_string_json string = beyond_uint32_string_t("value");
+        // created from its type rather than from a beyond_uint32_string_t:
+        // that would consider the std::filesystem::path conversion, which
+        // libstdc++ 10 cannot decide for a class derived from std::string
+        const beyond_uint32_string_json string(beyond_uint32_string_json::value_t::string);
         CHECK_THROWS_WITH_AS(beyond_uint32_string_json::to_msgpack(string), expected, beyond_uint32_string_json::out_of_range&);
     }
 #endif