diff --git a/src/System.CommandLine/Option.cs b/src/System.CommandLine/Option.cs
index b8fd96a77f..77ff4c47c1 100644
--- a/src/System.CommandLine/Option.cs
+++ b/src/System.CommandLine/Option.cs
@@ -169,7 +169,7 @@ public string? ArgumentHelpName
         public virtual ArgumentArity Arity
         {
             get => Argument.Arity;
-            init
+            set
             {
                 if (value.MaximumNumberOfValues > 0)
                 {
diff --git a/src/System.CommandLine/Option{T}.cs b/src/System.CommandLine/Option{T}.cs
index d5e3e82bfe..0d890c814b 100644
--- a/src/System.CommandLine/Option{T}.cs
+++ b/src/System.CommandLine/Option{T}.cs
@@ -65,7 +65,7 @@ public Option(
         public override ArgumentArity Arity
         {
             get => base.Arity;
-            init => Argument.Arity = value;
+            set => Argument.Arity = value;
         }
     }
 }
\ No newline at end of file