And https://gcc.gnu.org/onlinedocs/cpp/Defined.html says defined is not needed.

> Conditionals written like this:
>
>      #if defined BUFSIZE && BUFSIZE >= 1024
>
> can generally be simplified to just #if BUFSIZE >= 1024, since if BUFSIZE is not defined, it will be interpreted as having the value zero.

src/dnssec/lib/binary.c

@@ -25,7 +25,7 @@
 #include "error.h"
 #include "shared.h"
 
-#if defined (NETTLE_VERSION_MAJOR) && NETTLE_VERSION_MAJOR >= 3
+#if NETTLE_VERSION_MAJOR >= 3
 typedef size_t nettle_len;
 #else
 typedef unsigned nettle_len;