diff --git a/bet/calculateP/calculateP.py b/bet/calculateP/calculateP.py
index 9aee3a02..579c0483 100644
--- a/bet/calculateP/calculateP.py
+++ b/bet/calculateP/calculateP.py
@@ -424,7 +424,9 @@ def exact_volume_1D(samples, input_domain, distribution='uniform', a=None,
         edges = scipy.stats.beta.cdf(edges, a=a, b=b,
                 loc=input_domain[:, 0], scale=domain_width)
     # calculate difference between right and left of each cell and renormalize
-    lam_vol = np.squeeze(edges[1:, :] - edges[:-1, :])
+    sorted_lam_vol = np.squeeze(edges[1:, :] - edges[:-1, :])
+    lam_vol = np.zeros(sorted_lam_vol.shape)
+    lam_vol[sort_ind] = sorted_lam_vol
     if distribution == 'uniform':
         lam_vol = lam_vol/domain_width
     # Set up local arrays for parallelism