diff --git a/pyerrors/obs.py b/pyerrors/obs.py
index b3c51e0f..2dcab477 100644
--- a/pyerrors/obs.py
+++ b/pyerrors/obs.py
@@ -290,7 +290,8 @@ class Obs:
 
             def _compute_drho(i):
                 tmp = (self.e_rho[e_name][i + 1:w_max]
-                       + np.concatenate([self.e_rho[e_name][i - 1:None if i - w_max // 2 < 0 else 2 * (i - w_max // 2):-1], self.e_rho[e_name][1:max(1, w_max - 2 * i)]])
+                       + np.concatenate([self.e_rho[e_name][i - 1:None if i - w_max // 2 < 0 else 2 * (i - w_max // 2):-1],
+                                         self.e_rho[e_name][1:max(1, w_max - 2 * i)]])
                        - 2 * self.e_rho[e_name][i] * self.e_rho[e_name][1:w_max - i])
                 self.e_drho[e_name][i] = np.sqrt(np.sum(tmp ** 2) / e_N)