1 files changed, 2 insertions, 2 deletions
diff --git a/src/ProtocolBuffers/GeneratedMessage.cs b/src/ProtocolBuffers/GeneratedMessage.cs
index d8747599..055bc722 100644
--- a/src/ProtocolBuffers/GeneratedMessage.cs
+++ b/src/ProtocolBuffers/GeneratedMessage.cs
@@ -66,8 +66,8 @@ namespace Google.ProtocolBuffers {
 
     internal IDictionary<FieldDescriptor, Object> GetMutableFieldMap() {
 
-      // Use a SortedList so we'll end up serializing fields in order
-      var ret = new SortedList<FieldDescriptor, object>();
+      // Use a SortedDictionary so we'll end up serializing fields in order
+      var ret = new SortedDictionary<FieldDescriptor, object>();
       MessageDescriptor descriptor = DescriptorForType;
       foreach (FieldDescriptor field in descriptor.Fields) {
         IFieldAccessor<TMessage, TBuilder> accessor = InternalFieldAccessors[field];