diff --git a/include/nlohmann/detail/output/binary_writer.hpp b/include/nlohmann/detail/output/binary_writer.hpp
index 24426d48..770c7dd3 100644
--- a/include/nlohmann/detail/output/binary_writer.hpp
+++ b/include/nlohmann/detail/output/binary_writer.hpp
@@ -723,14 +723,42 @@ class binary_writer
 
     std::size_t write_bson_integer(const typename BasicJsonType::string_t& name, const BasicJsonType& j)
     {
-        if (j.m_value.number_integer <= static_cast<uint64_t>((std::numeric_limits<int32_t>::max)()))
+        auto n = j.m_value.number_integer;
+        if ((std::numeric_limits<int32_t>::min)() <= n and n <= (std::numeric_limits<int32_t>::max)())
         {
             oa->write_character(static_cast<CharType>(0x10)); // int32
             oa->write_characters(
                 reinterpret_cast<const CharType*>(name.c_str()),
                 name.size() + 1u);
 
-            write_number_little_endian(static_cast<std::int32_t>(j.m_value.number_integer));
+            write_number_little_endian(static_cast<std::int32_t>(n));
+
+            return /*id*/ 1ul + name.size() + 1ul + sizeof(std::int32_t);
+        }
+        else
+        {
+            oa->write_character(static_cast<CharType>(0x12)); // int64
+            oa->write_characters(
+                reinterpret_cast<const CharType*>(name.c_str()),
+                name.size() + 1u);
+
+            write_number_little_endian(static_cast<std::int64_t>(j.m_value.number_integer));
+
+            return /*id*/ 1ul + name.size() + 1ul + sizeof(std::int64_t);
+        }
+    }
+
+    std::size_t write_bson_unsigned(const typename BasicJsonType::string_t& name, const BasicJsonType& j)
+    {
+        auto n = j.m_value.number_integer;
+        if (n <= static_cast<uint64_t>((std::numeric_limits<uint32_t>::max)()))
+        {
+            oa->write_character(static_cast<CharType>(0x10)); // int32
+            oa->write_characters(
+                reinterpret_cast<const CharType*>(name.c_str()),
+                name.size() + 1u);
+
+            write_number_little_endian(static_cast<std::int32_t>(n));
 
             return /*id*/ 1ul + name.size() + 1ul + sizeof(std::int32_t);
         }
@@ -760,6 +788,8 @@ class binary_writer
                 return write_bson_double(name, j);
             case value_t::number_integer:
                 return write_bson_integer(name, j);
+            case value_t::number_unsigned:
+                return write_bson_unsigned(name, j);
             case value_t::string:
                 return write_bson_string(name, j);
             case value_t::null:
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index c564e57f..fa1d8e39 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -8557,14 +8557,42 @@ class binary_writer
 
     std::size_t write_bson_integer(const typename BasicJsonType::string_t& name, const BasicJsonType& j)
     {
-        if (j.m_value.number_integer <= static_cast<uint64_t>((std::numeric_limits<int32_t>::max)()))
+        auto n = j.m_value.number_integer;
+        if ((std::numeric_limits<int32_t>::min)() <= n and n <= (std::numeric_limits<int32_t>::max)())
         {
             oa->write_character(static_cast<CharType>(0x10)); // int32
             oa->write_characters(
                 reinterpret_cast<const CharType*>(name.c_str()),
                 name.size() + 1u);
 
-            write_number_little_endian(static_cast<std::int32_t>(j.m_value.number_integer));
+            write_number_little_endian(static_cast<std::int32_t>(n));
+
+            return /*id*/ 1ul + name.size() + 1ul + sizeof(std::int32_t);
+        }
+        else
+        {
+            oa->write_character(static_cast<CharType>(0x12)); // int64
+            oa->write_characters(
+                reinterpret_cast<const CharType*>(name.c_str()),
+                name.size() + 1u);
+
+            write_number_little_endian(static_cast<std::int64_t>(j.m_value.number_integer));
+
+            return /*id*/ 1ul + name.size() + 1ul + sizeof(std::int64_t);
+        }
+    }
+
+    std::size_t write_bson_unsigned(const typename BasicJsonType::string_t& name, const BasicJsonType& j)
+    {
+        auto n = j.m_value.number_integer;
+        if (n <= static_cast<uint64_t>((std::numeric_limits<uint32_t>::max)()))
+        {
+            oa->write_character(static_cast<CharType>(0x10)); // int32
+            oa->write_characters(
+                reinterpret_cast<const CharType*>(name.c_str()),
+                name.size() + 1u);
+
+            write_number_little_endian(static_cast<std::int32_t>(n));
 
             return /*id*/ 1ul + name.size() + 1ul + sizeof(std::int32_t);
         }
@@ -8594,6 +8622,8 @@ class binary_writer
                 return write_bson_double(name, j);
             case value_t::number_integer:
                 return write_bson_integer(name, j);
+            case value_t::number_unsigned:
+                return write_bson_unsigned(name, j);
             case value_t::string:
                 return write_bson_string(name, j);
             case value_t::null:
diff --git a/test/src/unit-bson.cpp b/test/src/unit-bson.cpp
index 73989769..8de05e80 100644
--- a/test/src/unit-bson.cpp
+++ b/test/src/unit-bson.cpp
@@ -279,5 +279,77 @@ TEST_CASE("BSON")
             CHECK(json::from_bson(result, true, false) == j);
         }
 
+        SECTION("non-empty object with negative integer (32-bit) member")
+        {
+            json j =
+            {
+                { "entry", std::int32_t{-1} }
+            };
+
+            std::vector<uint8_t> expected =
+            {
+                0x10, 0x00, 0x00, 0x00, // size (little endian)
+                0x10, /// entry: int32
+                'e', 'n', 't', 'r', 'y', '\x00',
+                0xFF, 0xFF, 0xFF, 0xFF,
+                0x00 // end marker
+            };
+
+            const auto result = json::to_bson(j);
+            CHECK(result == expected);
+
+            // roundtrip
+            CHECK(json::from_bson(result) == j);
+            CHECK(json::from_bson(result, true, false) == j);
+        }
+
+        SECTION("non-empty object with negative integer (64-bit) member")
+        {
+            json j =
+            {
+                { "entry", std::int64_t{-1} }
+            };
+
+            std::vector<uint8_t> expected =
+            {
+                0x10, 0x00, 0x00, 0x00, // size (little endian)
+                0x10, /// entry: int32
+                'e', 'n', 't', 'r', 'y', '\x00',
+                0xFF, 0xFF, 0xFF, 0xFF,
+                0x00 // end marker
+            };
+
+            const auto result = json::to_bson(j);
+            CHECK(result == expected);
+
+            // roundtrip
+            CHECK(json::from_bson(result) == j);
+            CHECK(json::from_bson(result, true, false) == j);
+        }
+
+        SECTION("non-empty object with unsigned integer (64-bit) member")
+        {
+            // directly encoding uint64 is not supported in bson (only for timestamp values)
+            json j =
+            {
+                { "entry", std::uint64_t{0x1234567804030201} }
+            };
+
+            std::vector<uint8_t> expected =
+            {
+                0x14, 0x00, 0x00, 0x00, // size (little endian)
+                0x12, /// entry: int64
+                'e', 'n', 't', 'r', 'y', '\x00',
+                0x01, 0x02, 0x03, 0x04, 0x78, 0x56, 0x34, 0x12,
+                0x00 // end marker
+            };
+
+            const auto result = json::to_bson(j);
+            CHECK(result == expected);
+
+            // roundtrip
+            CHECK(json::from_bson(result) == j);
+            CHECK(json::from_bson(result, true, false) == j);
+        }
     }
 }