diff --git a/CHANGELOG.md b/CHANGELOG.md
index fa172799..e84de962 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -51,6 +51,10 @@
 
 * **FIX** links in the documention to always point to the most recent version of the pre-builts (#218).
 
+### Fixed (workflow)
+
+* **FIX** fixed optimisation tolerance of hydro power plants from xtol to xatol (#266).
+
 ## 1.1.0 (2021-12-22)
 
 This version is a minor update to v1.0. It comes with updated input data, updated dependencies, several convenience features, several optional overrides, and with massively extended documentation. You should not expect model results to deviate much from v1.0.
diff --git a/scripts/hydro/inflow_mwh.py b/scripts/hydro/inflow_mwh.py
index 0c04f94d..9f7d19a8 100644
--- a/scripts/hydro/inflow_mwh.py
+++ b/scripts/hydro/inflow_mwh.py
@@ -86,7 +86,7 @@ def residual(scaling_factor):
         return abs(generation(scaling_factor).sum() - annual_generation)
 
     x0 = annual_generation / inflow_m3.sum()
-    res = minimize(residual, x0, method='nelder-mead', options={'xtol': 1e-10})
+    res = minimize(residual, x0, method='nelder-mead', options={'xatol': 1e-10})
     assert res.success, print(res)
     assert res.fun < 1, print(res) # error smaller than 1 MWh