diff --git a/fdm.c b/fdm.c
index e6f955cc..746a6d59 100644
--- a/fdm.c
+++ b/fdm.c
@@ -97,12 +97,14 @@ bool
 fdm_add(struct fdm *fdm, int fd, int events, fdm_handler_t handler, void *data)
 {
 #if defined(_DEBUG)
+#ifdef __FreeBSD__
     int flags = fcntl(fd, F_GETFL);
     if (!(flags & O_NONBLOCK)) {
         LOG_ERR("FD=%d is in blocking mode", fd);
         assert(false);
         return false;
     }
+#endif
 
     tll_foreach(fdm->fds, it) {
         if (it->item->fd == fd) {