diff --git a/docs/requirements.txt b/docs/requirements.txt
index 84652fb..41b7a9b 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -3,4 +3,7 @@ torch
 scipy
 matplotlib
 tifffile
-myst_parser
\ No newline at end of file
+myst_parser
+sphinx==5.3.0
+sphinx_rtd_theme==1.1.1
+readthedocs-sphinx-search==0.1.1
\ No newline at end of file
diff --git a/taufactor/taufactor.py b/taufactor/taufactor.py
index d18ed9e..9ded7f2 100644
--- a/taufactor/taufactor.py
+++ b/taufactor/taufactor.py
@@ -198,7 +198,7 @@ def check_vertical_flux(self, conv_crit):
         vert_flux[self.conc[:, :-2, 1:-1, 1:-1] == 0] = 0
         vert_flux[self.conc[:, 1:-1, 1:-1, 1:-1] == 0] = 0
         fl = torch.sum(vert_flux, (0, 2, 3))[1:-1]
-        err = (fl.max() - fl.min())*2/(fl.max() + fl.min())
+        err = (fl.max() - fl.min())/(fl.max())
         if fl.min() == 0:
             return 'zero_flux', torch.mean(fl), err
         if err < conv_crit or torch.isnan(err).item():