diff --git a/pyerrors/obs.py b/pyerrors/obs.py
index 03486f14..c8373d5e 100644
--- a/pyerrors/obs.py
+++ b/pyerrors/obs.py
@@ -305,7 +305,7 @@ class Obs:
                         self.e_dtauint[e_name] = np.sqrt(self.e_n_dtauint[e_name][n] ** 2 + texp ** 2 * self.e_drho[e_name][n + 1] ** 2)
                         # Error of tau_exp neglected so far, missing term: self.e_rho[e_name][n + 1] ** 2 * d_tau_exp ** 2
                         self.e_dvalue[e_name] = np.sqrt(2 * self.e_tauint[e_name] * e_gamma[e_name][0] * (1 + 1 / e_N) / e_N)
-                        self.e_ddvalue[e_name] = self.e_dvalue[e_name] * np.sqrt((n + 0.5) / e_N)
+                        self.e_ddvalue[e_name] = self.e_dvalue[e_name] * np.sqrt((n / gapsize + 0.5) / e_N)
                         self.e_windowsize[e_name] = n
                         break
             else:
@@ -327,7 +327,7 @@ class Obs:
                             self.e_tauint[e_name] = self.e_n_tauint[e_name][n] * (1 + (2 * n / gapsize + 1) / e_N) / (1 + 1 / e_N)  # Bias correction hep-lat/0306017 eq. (49)
                             self.e_dtauint[e_name] = self.e_n_dtauint[e_name][n]
                             self.e_dvalue[e_name] = np.sqrt(2 * self.e_tauint[e_name] * e_gamma[e_name][0] * (1 + 1 / e_N) / e_N)
-                            self.e_ddvalue[e_name] = self.e_dvalue[e_name] * np.sqrt((n + 0.5) / e_N)
+                            self.e_ddvalue[e_name] = self.e_dvalue[e_name] * np.sqrt((n / gapsize + 0.5) / e_N)
                             self.e_windowsize[e_name] = n
                             break