diff --git a/src/lib9/ffork-FreeBSD.c b/src/lib9/ffork-FreeBSD.c
new file mode 100644
index 0000000..a7c82e6
--- /dev/null
+++ b/src/lib9/ffork-FreeBSD.c
@@ -0,0 +1,33 @@
+#include <lib9.h>
+
+extern int __isthreaded;
+int
+ffork(int flags, void(*fn)(void*), void *arg)
+{
+	void *p;
+
+	__isthreaded = 1;
+	p = malloc(16384);
+	if(p == nil)
+		return -1;
+	memset(p, 0xFE, 16384);
+	return rfork_thread(RFPROC|flags, (char*)p+16000, (int(*)(void*))fn, arg);
+}
+
+/*
+ * For FreeBSD libc.
+ */
+
+typedef struct {
+	volatile long	access_lock;
+	volatile long	lock_owner;
+	volatile char	*fname;
+	volatile int	lineno;
+} spinlock_t;
+
+void
+_spinlock(spinlock_t *lk)
+{
+	lock((Lock*)&lk->access_lock);
+}
+