diff --git a/scripts/solve_network.py b/scripts/solve_network.py
index 11de6151..8a577e23 100644
--- a/scripts/solve_network.py
+++ b/scripts/solve_network.py
@@ -735,9 +735,9 @@ def add_operational_reserve_margin(n, sns, config):
             .loc[vres_i.intersection(ext_i)]
             .rename({"Generator-ext": "Generator"})
         )
-        lhs = summed_reserve + (p_nom_vres * (-EPSILON_VRES * capacity_factor)).sum(
-            "Generator"
-        )
+        lhs = summed_reserve + (
+            p_nom_vres * (-EPSILON_VRES * xr.DataArray(capacity_factor))
+        ).sum("Generator")
 
     # Total demand per t
     demand = get_as_dense(n, "Load", "p_set").sum(axis=1)
@@ -767,7 +767,7 @@ def add_operational_reserve_margin(n, sns, config):
 
     p_max_pu = get_as_dense(n, "Generator", "p_max_pu")
 
-    lhs = dispatch + reserve - capacity_variable * p_max_pu[ext_i]
+    lhs = dispatch + reserve - capacity_variable * xr.DataArray(p_max_pu[ext_i])
 
     rhs = (p_max_pu[fix_i] * capacity_fixed).reindex(columns=gen_i, fill_value=0)