diff --git a/csharp/Lib/Units/Power/ActivePower.cs b/csharp/Lib/Units/Power/ActivePower.cs
index f451d4f79..6d859ad50 100644
--- a/csharp/Lib/Units/Power/ActivePower.cs
+++ b/csharp/Lib/Units/Power/ActivePower.cs
@@ -12,6 +12,6 @@ public sealed class ActivePower : AcPower
     public static implicit operator ActivePower(Double d) => new ActivePower(d);
     public static implicit operator Double(ActivePower d) => d.Value;
     
-    public static ActivePower operator -(ActivePower d) => -d.Value;
+    public static ActivePower? operator -(ActivePower? d) => -d?.Value;
 }
 
diff --git a/csharp/Lib/Units/Power/ReactivePower.cs b/csharp/Lib/Units/Power/ReactivePower.cs
index 28238d62a..5c54095ab 100644
--- a/csharp/Lib/Units/Power/ReactivePower.cs
+++ b/csharp/Lib/Units/Power/ReactivePower.cs
@@ -10,5 +10,7 @@ public sealed class ReactivePower : AcPower
     
     public static implicit operator ReactivePower(Double d) => new ReactivePower(d);
     public static implicit operator Double(ReactivePower d) => d.Value;
+    
+    public static ReactivePower? operator -(ReactivePower? d) => -d?.Value;
 }