diff --git a/src/core/Microsoft.Dynamic/Microsoft.Dynamic.csproj b/src/core/Microsoft.Dynamic/Microsoft.Dynamic.csproj
index cbe94451..99251395 100644
--- a/src/core/Microsoft.Dynamic/Microsoft.Dynamic.csproj
+++ b/src/core/Microsoft.Dynamic/Microsoft.Dynamic.csproj
@@ -10,6 +10,8 @@
     <MeziantouPolyfill_IncludedPolyfills>
       P:System.Collections.ObjectModel.ReadOnlyCollection`1.Empty;
       P:System.Collections.ObjectModel.ReadOnlyDictionary`2.Empty;
+      M:System.String.IndexOf(System.Char,System.StringComparison);
+      M:System.String.StartsWith(System.Char);
     </MeziantouPolyfill_IncludedPolyfills>
   </PropertyGroup>
 
diff --git a/src/core/Microsoft.Dynamic/StringExtensions.cs b/src/core/Microsoft.Dynamic/StringExtensions.cs
deleted file mode 100644
index a1963924..00000000
--- a/src/core/Microsoft.Dynamic/StringExtensions.cs
+++ /dev/null
@@ -1,24 +0,0 @@
-using System;
-
-namespace Microsoft.Scripting
-{
-    internal static class StringExtensions
-    {
-#if !NETCOREAPP
-        public static bool EndsWith(this string str, char value)
-        {
-            return str.EndsWith(value.ToString(), StringComparison.Ordinal);
-        }
-
-        public static bool StartsWith(this string str, char value)
-        {
-            return str.StartsWith(value.ToString(), StringComparison.Ordinal);
-        }
-
-        public static int IndexOf(this string str, char value, StringComparison comparisonType) {
-            if (comparisonType == StringComparison.Ordinal) return str.IndexOf(value);
-            return str.IndexOf(value.ToString(), comparisonType);
-        }
-#endif
-    }
-}