--- a/src/_csrc/portable_endian.h
+++ b/src/_csrc/portable_endian.h
@@ -98,7 +98,7 @@
 
 #   include <endian.h>
 
-#elif defined(__NetBSD__) || defined(__FreeBSD__) || defined(__DragonFly__)
+#elif defined(__NetBSD__) || defined(__FreeBSD__) || defined(__DragonFly__) || defined(__FreeBSD_kernel__)
 
 #   include <sys/endian.h>
 
