diff --git a/docs/mkdocs/docs/home/exceptions.md b/docs/mkdocs/docs/home/exceptions.md
index 21f1d0c7a7..1b8d7ef83f 100644
--- a/docs/mkdocs/docs/home/exceptions.md
+++ b/docs/mkdocs/docs/home/exceptions.md
@@ -839,7 +839,7 @@ A parsed number could not be stored as without changing it to NaN or INF.
 
 ### json.exception.out_of_range.407
 
-UBJSON only support integer numbers up to 9223372036854775807.
+UBJSON only supports integer numbers up to 9223372036854775807.
 
 !!! failure "Example message"
 
diff --git a/include/nlohmann/detail/input/binary_reader.hpp b/include/nlohmann/detail/input/binary_reader.hpp
index e3885f2c03..21b40f8996 100644
--- a/include/nlohmann/detail/input/binary_reader.hpp
+++ b/include/nlohmann/detail/input/binary_reader.hpp
@@ -322,17 +322,18 @@ class binary_reader
                 return get_number<std::int32_t, true>(input_format_t::bson, value) && sax->number_integer(value);
             }
 
+            case 0x11: // uint64
+            {
+                std::uint64_t value{};
+                return get_number<std::uint64_t, true>(input_format_t::bson, value) && sax->number_unsigned(value);
+            }
+
             case 0x12: // int64
             {
                 std::int64_t value{};
                 return get_number<std::int64_t, true>(input_format_t::bson, value) && sax->number_integer(value);
             }
 
-            case 0x11: // uint64
-            {
-                std::uint64_t value{};
-                return get_number<std::uint64_t, true>(input_format_t::bson, value) && sax->number_unsigned(value);
-            }
 
             default: // anything else not supported (yet)
             {
diff --git a/include/nlohmann/detail/output/binary_writer.hpp b/include/nlohmann/detail/output/binary_writer.hpp
index f1a930996f..6dff77a8cd 100644
--- a/include/nlohmann/detail/output/binary_writer.hpp
+++ b/include/nlohmann/detail/output/binary_writer.hpp
@@ -1076,7 +1076,7 @@ class binary_writer
     {
         return (value <= static_cast<std::uint64_t>((std::numeric_limits<std::int32_t>::max)()))
                ? sizeof(std::int32_t)
-               : sizeof(std::int64_t);
+               : sizeof(std::uint64_t);
     }
 
     /*!
@@ -1090,11 +1090,6 @@ class binary_writer
             write_bson_entry_header(name, 0x10 /* int32 */);
             write_number<std::int32_t>(static_cast<std::int32_t>(j.m_data.m_value.number_unsigned), true);
         }
-        else if (j.m_data.m_value.number_unsigned <= static_cast<std::uint64_t>((std::numeric_limits<std::int64_t>::max)()))
-        {
-            write_bson_entry_header(name, 0x12 /* int64 */);
-            write_number<std::int64_t>(static_cast<std::int64_t>(j.m_data.m_value.number_unsigned), true);
-        }
         else
         {
             write_bson_entry_header(name, 0x11 /* uint64 */);
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 14a16cefa8..e000f94a28 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -10000,17 +10000,18 @@ class binary_reader
                 return get_number<std::int32_t, true>(input_format_t::bson, value) && sax->number_integer(value);
             }
 
+            case 0x11: // uint64
+            {
+                std::uint64_t value{};
+                return get_number<std::uint64_t, true>(input_format_t::bson, value) && sax->number_unsigned(value);
+            }
+
             case 0x12: // int64
             {
                 std::int64_t value{};
                 return get_number<std::int64_t, true>(input_format_t::bson, value) && sax->number_integer(value);
             }
 
-            case 0x11: // uint64
-            {
-                std::uint64_t value{};
-                return get_number<std::uint64_t, true>(input_format_t::bson, value) && sax->number_unsigned(value);
-            }
 
             default: // anything else not supported (yet)
             {
@@ -16718,7 +16719,7 @@ class binary_writer
     {
         return (value <= static_cast<std::uint64_t>((std::numeric_limits<std::int32_t>::max)()))
                ? sizeof(std::int32_t)
-               : sizeof(std::int64_t);
+               : sizeof(std::uint64_t);
     }
 
     /*!
@@ -16732,11 +16733,6 @@ class binary_writer
             write_bson_entry_header(name, 0x10 /* int32 */);
             write_number<std::int32_t>(static_cast<std::int32_t>(j.m_data.m_value.number_unsigned), true);
         }
-        else if (j.m_data.m_value.number_unsigned <= static_cast<std::uint64_t>((std::numeric_limits<std::int64_t>::max)()))
-        {
-            write_bson_entry_header(name, 0x12 /* int64 */);
-            write_number<std::int64_t>(static_cast<std::int64_t>(j.m_data.m_value.number_unsigned), true);
-        }
         else
         {
             write_bson_entry_header(name, 0x11 /* uint64 */);
diff --git a/tests/src/unit-bson.cpp b/tests/src/unit-bson.cpp
index e35c338960..970ad509d7 100644
--- a/tests/src/unit-bson.cpp
+++ b/tests/src/unit-bson.cpp
@@ -339,7 +339,7 @@ TEST_CASE("BSON")
             std::vector<std::uint8_t> const expected =
             {
                 0x14, 0x00, 0x00, 0x00, // size (little endian)
-                0x12, /// entry: int64
+                0x11, /// entry: uint64
                 'e', 'n', 't', 'r', 'y', '\x00',
                 0x01, 0x02, 0x03, 0x04, 0x78, 0x56, 0x34, 0x12,
                 0x00 // end marker
@@ -1132,7 +1132,7 @@ TEST_CASE("BSON numerical data")
                     std::vector<std::uint8_t> const expected_bson =
                     {
                         0x14u, 0x00u, 0x00u, 0x00u, // size (little endian)
-                        0x12u, /// entry: int64
+                        0x11u, /// entry: uint64
                         'e', 'n', 't', 'r', 'y', '\x00',
                         static_cast<std::uint8_t>((iu >> (8u * 0u)) & 0xffu),
                         static_cast<std::uint8_t>((iu >> (8u * 1u)) & 0xffu),