diff --git a/multimedia/mkvtoolnix/files/patch-lib_fmt_include_fmt_format.h b/multimedia/mkvtoolnix/files/patch-lib_fmt_include_fmt_format.h
new file mode 100644
index 000000000000..a8ecd4b0096d
--- /dev/null
+++ b/multimedia/mkvtoolnix/files/patch-lib_fmt_include_fmt_format.h
@@ -0,0 +1,10 @@
+--- lib/fmt/include/fmt/format.h.orig	2026-01-02 12:35:10 UTC
++++ lib/fmt/include/fmt/format.h
+@@ -44,6 +44,7 @@
+ #  include <cmath>    // std::signbit
+ #  include <cstddef>  // std::byte
+ #  include <cstdint>  // uint32_t
++#  include <cstdlib>  // malloc/free
+ #  include <cstring>  // std::memcpy
+ #  include <limits>   // std::numeric_limits
+ #  include <new>      // std::bad_alloc