diff --git a/scripts/add_electricity.py b/scripts/add_electricity.py
index 85391a64..d2a61fb5 100755
--- a/scripts/add_electricity.py
+++ b/scripts/add_electricity.py
@@ -498,7 +498,7 @@ def attach_hydro(n, costs, ppl, profile_hydro, hydro_capacities, carriers, **con
         e_target = hydro_stats["E_store[TWh]"].clip(lower=0.2) * 1e6
         e_installed = hydro.eval("p_nom * max_hours").groupby(hydro.country).sum()
         e_missing = e_target - e_installed
-        missing_mh_i = hydro.query("max_hours == 0").index
+        missing_mh_i = hydro.query("max_hours.isnull()").index
 
         if hydro_max_hours == "energy_capacity_totals_by_country":
             # watch out some p_nom values like IE's are totally underrepresented
@@ -511,6 +511,8 @@ def attach_hydro(n, costs, ppl, profile_hydro, hydro_capacities, carriers, **con
                 hydro_stats["E_store[TWh]"] * 1e3 / hydro_stats["p_nom_discharge[GW]"]
             )
 
+        max_hours_country.clip(0, inplace = True)
+        
         missing_countries = pd.Index(hydro["country"].unique()).difference(
             max_hours_country.dropna().index
         )