diff --git a/src/Polyfill/Polyfill_StringBuilder.cs b/src/Polyfill/Polyfill_StringBuilder.cs
index 54b50a1e..8863614f 100644
--- a/src/Polyfill/Polyfill_StringBuilder.cs
+++ b/src/Polyfill/Polyfill_StringBuilder.cs
@@ -7,8 +7,6 @@
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Text;
-using System.Threading;
-using System.Threading.Tasks;
 using Link = System.ComponentModel.DescriptionAttribute;
 
 static partial class Polyfill