diff --git a/src/anromero/spectral-sequences.lisp b/src/anromero/spectral-sequences.lisp
index f7ba8ec..7c22035 100644
--- a/src/anromero/spectral-sequences.lisp
+++ b/src/anromero/spectral-sequences.lisp
@@ -1599,9 +1599,18 @@
                                                           )))))
     (the list
       (if pos (fourth (nth pos rslts))
-        (let ((l (spsq-dffr-mtrx fltrcm r p q )))
-          (declare (type list l))
+        (let* ((aux (spsq-dffr-mtrx fltrcm r p q ))
+               (l nil)
+               (nrow (length (first aux)))
+               (ncol (length aux)))
+          (declare (type list aux l)
+                   (fixnum nrow ncol))
           (progn
+            (dotimes (i nrow)
+              (let ((rowi nil))
+                (dotimes (j ncol)
+                  (push (nth (1- (- nrow i)) (nth (1- (- ncol j)) aux)) rowi))
+                (push rowi l)))
             (push (list r p q l) rslts)
             (setf (slot-value ss 'dffr-rslts) rslts)
             l))))))