diff --git a/test/python/analyse_block_structure_from_gf2.py b/test/python/analyse_block_structure_from_gf2.py
index d08dad30..25806815 100644
--- a/test/python/analyse_block_structure_from_gf2.py
+++ b/test/python/analyse_block_structure_from_gf2.py
@@ -90,7 +90,8 @@ Gt = BlockGf(name_block_generator = [(name,
 
 known_moments = np.zeros((2,10,10), dtype=np.complex)
 known_moments[1,:] = np.eye(10)
-Gt['ud'].set_from_fourier(G['ud'], known_moments)
+tail, err = fit_tail(G['ud'], known_moments)
+Gt['ud'].set_from_fourier(G['ud'], tail)
 
 G_new = SK.analyse_block_structure_from_gf([Gt])
 G_new_symm = G_new[0].copy()