diff --git a/CliFx/CliFx.csproj b/CliFx/CliFx.csproj
index b77c5a3..f244ebb 100644
--- a/CliFx/CliFx.csproj
+++ b/CliFx/CliFx.csproj
@@ -27,7 +27,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="all" />
-    <PackageReference Include="Nullable" Version="1.3.1" PrivateAssets="all" />
+    <PackageReference Include="PolySharp" Version="1.8.1" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
diff --git a/CliFx/Input/CommandInput.cs b/CliFx/Input/CommandInput.cs
index ed52f6e..9820b69 100644
--- a/CliFx/Input/CommandInput.cs
+++ b/CliFx/Input/CommandInput.cs
@@ -153,7 +153,7 @@ internal partial class CommandInput
                 if (!string.IsNullOrWhiteSpace(lastOptionIdentifier))
                     result.Add(new OptionInput(lastOptionIdentifier, lastOptionValues));
 
-                lastOptionIdentifier = argument.Substring(2);
+                lastOptionIdentifier = argument[2..];
                 lastOptionValues = new List<string>();
             }
             // Short name
@@ -161,7 +161,7 @@ internal partial class CommandInput
                      argument.Length > 1 &&
                      char.IsLetter(argument[1]))
             {
-                foreach (var alias in argument.Substring(1))
+                foreach (var alias in argument[1..])
                 {
                     // Flush previous
                     if (!string.IsNullOrWhiteSpace(lastOptionIdentifier))