diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_AFUNIX_H.h b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_AFUNIX_H.h
new file mode 100644
index 0000000..a02827e
--- /dev/null
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_AFUNIX_H.h
@@ -0,0 +1,20 @@
+// HAVE_AFUNIX_H
+
+#undef HAVE_AFUNIX_H
+
+/* Note that __MINGW32_*_VERSION seems to be frozen and so cannot be used
+ * for this check. Which means this header is never available on 32-bit
+ * MinGW.
+ */
+
+#ifdef _MSC_VER
+#  include <sdkddkver.h>
+#  if defined(WDK_NTDDI_VERSION) && WDK_NTDDI_VERSION >= NTDDI_WIN10_19H1
+#    define HAVE_AFUNIX_H 1
+#  endif
+#elif defined(__MINGW64__)
+#  include <stddef.h>
+#  if defined(__MINGW64_MAJOR_VERSION) && __MINGW64_MAJOR_VERSION >= 11
+#    define HAVE_AFUNIX_H 1
+#  endif
+#endif