diff --git a/io.c b/io.c
index 2731bb829f..1074689560 100644
--- a/io.c
+++ b/io.c
@@ -1775,6 +1775,7 @@ io_fillbuf(rb_io_t *fptr)
 		rb_syserr_fail_path(e, path);
 	    }
         }
+	if (r > 0) rb_io_check_closed(fptr);
         fptr->rbuf.off = 0;
         fptr->rbuf.len = (int)r; /* r should be <= rbuf_capa */
         if (r == 0)