diff --git a/src/unix/fs.c b/src/unix/fs.c
index 52082e93..d739c282 100644
--- a/src/unix/fs.c
+++ b/src/unix/fs.c
@@ -574,7 +574,14 @@ static ssize_t uv__fs_sendfile(uv_fs_t* req) {
     r = sendfile(in_fd, out_fd, req->off, &len, NULL, 0);
 #endif
 
-    if (r != -1 || len != 0) {
+     /*
+     * The man page for sendfile(2) on DragonFly states that `len` contains
+     * a meaningful value ONLY in case of EAGAIN and EINTR.
+     * Nothing is said about it's value in case of other errors, so better
+     * not depend on the potential wrong assumption that is was not modified
+     * by the syscall.
+     */
+    if (r == 0 || ((errno == EAGAIN || errno == EINTR) && len != 0)) {
       req->off += len;
       return (ssize_t) len;
     }