diff --git a/Antlr4.Runtime/Atn/SemanticContext.cs b/Antlr4.Runtime/Atn/SemanticContext.cs
index a0a53e2bc..888cf39d1 100644
--- a/Antlr4.Runtime/Atn/SemanticContext.cs
+++ b/Antlr4.Runtime/Atn/SemanticContext.cs
@@ -27,6 +27,7 @@
  *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
+using System;
 using System.Collections.Generic;
 using Antlr4.Runtime;
 using Antlr4.Runtime.Atn;
diff --git a/reference/sharpen-all-options.txt b/reference/sharpen-all-options.txt
index 7b24e9920..52377cbdc 100644
--- a/reference/sharpen-all-options.txt
+++ b/reference/sharpen-all-options.txt
@@ -99,6 +99,7 @@
 -methodMapping java.io.IOException.IOException(java.lang.Throwable) Sharpen.Extensions.CreateIOException
 -fieldMapping java.util.Locale.US InvariantCulture
 -typeMapping java.lang.Comparable System.IComparable
+-typeMapping java.lang.Comparable<> System.IComparable
 -typeMapping java.util.Comparator<> System.Collections.Generic.IComparer
 -typeMapping java.util.HashSet<> System.Collections.Generic.HashSet
 -typeMapping java.util.Set<> System.Collections.Generic.ISet