diff --git a/multimedia/dav1d/files/patch-freebsd12 b/multimedia/dav1d/files/patch-freebsd12
new file mode 100644
index 000000000000..6376c4a5a863
--- /dev/null
+++ b/multimedia/dav1d/files/patch-freebsd12
@@ -0,0 +1,19 @@
+Drop after FreeBSD 12.4 EOL around 2023-12-31
+FreeBSD >= 13.1 pulls cpu_set_t from <sched.h> via <pthread.h>
+
+https://cgit.freebsd.org/src/commit/?id=379bfb2aa9e9
+
+--- tests/checkasm/checkasm.c.orig	2023-02-14 16:39:08 UTC
++++ tests/checkasm/checkasm.c
+@@ -620,7 +620,11 @@ int main(int argc, char *argv[]) {
+                 fprintf(stderr, "checkasm: running on cpu %lu\n", affinity);
+             }
+ #elif defined(HAVE_PTHREAD_SETAFFINITY_NP) && defined(CPU_SET)
++#if defined(__FreeBSD__) && __FreeBSD__ < 13
++            cpuset_t set;
++#else
+             cpu_set_t set;
++#endif
+             CPU_ZERO(&set);
+             CPU_SET(affinity, &set);
+             if (pthread_setaffinity_np(pthread_self(), sizeof(set), &set)) {