diff --git a/example/eigen.py b/example/eigen.py
index 9c4e1ef..7ff9aed 100644
--- a/example/eigen.py
+++ b/example/eigen.py
@@ -22,7 +22,9 @@
 
 
 def check(mat):
-    return 'OK' if np.sum(mat - ref) == 0 else 'NOT OK'
+    return 'OK' if np.sum(abs(mat - ref)) == 0 else 'NOT OK'
+
+print("should_give_NOT_OK = %s" % check(ref[:, ::-1]))
 
 print("fixed_r = %s" % check(fixed_r()))
 print("fixed_c = %s" % check(fixed_c()))
diff --git a/example/eigen.ref b/example/eigen.ref
index bac73be..03091cc 100644
--- a/example/eigen.ref
+++ b/example/eigen.ref
@@ -1,3 +1,4 @@
+should_give_NOT_OK = NOT OK
 fixed_r = OK
 fixed_c = OK
 pt_r(fixed_r) = OK