diff --git a/include/nlohmann/detail/output/binary_writer.hpp b/include/nlohmann/detail/output/binary_writer.hpp
index 467346467a..342cb47845 100644
--- a/include/nlohmann/detail/output/binary_writer.hpp
+++ b/include/nlohmann/detail/output/binary_writer.hpp
@@ -279,6 +279,12 @@ class binary_writer
 
             case value_t::binary:
             {
+                if (j.m_value.binary->has_subtype())
+                {
+                    write_number(static_cast<std::uint8_t>(0xd8));
+                    write_number(j.m_value.binary->subtype());
+                }
+
                 // step 1: write control byte and the binary array size
                 const auto N = j.m_value.binary->size();
                 if (N <= 0x17)
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index cf41f741af..1d8b5fb612 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -12795,6 +12795,12 @@ class binary_writer
 
             case value_t::binary:
             {
+                if (j.m_value.binary->has_subtype())
+                {
+                    write_number(static_cast<std::uint8_t>(0xd8));
+                    write_number(j.m_value.binary->subtype());
+                }
+
                 // step 1: write control byte and the binary array size
                 const auto N = j.m_value.binary->size();
                 if (N <= 0x17)
diff --git a/test/src/unit-cbor.cpp b/test/src/unit-cbor.cpp
index 6af06bf60f..2aeac10d46 100644
--- a/test/src/unit-cbor.cpp
+++ b/test/src/unit-cbor.cpp
@@ -2503,6 +2503,8 @@ TEST_CASE("examples from RFC 7049 Appendix A")
         std::vector<uint8_t> expected((std::istreambuf_iterator<char>(f_bin)),
                                       std::istreambuf_iterator<char>());
         CHECK(j == json::binary(expected));
+
+        CHECK(json::to_cbor(json::binary(std::vector<uint8_t> {}, 0x42)) == std::vector<uint8_t> {0xd8, 0x42, 0x40});
     }
 
     SECTION("arrays")