diff --git a/src/language_server_api.h b/src/language_server_api.h
index 28e5877a..18863c71 100644
--- a/src/language_server_api.h
+++ b/src/language_server_api.h
@@ -260,7 +260,7 @@ MAKE_REFLECT_STRUCT(lsTextDocumentIdentifier, uri);
 struct lsVersionedTextDocumentIdentifier {
   lsDocumentUri uri;
   // The version number of this document.
-  int version = 0;
+  optional<int> version;
 
   lsTextDocumentIdentifier AsTextDocumentIdentifier() const;
 };
@@ -990,9 +990,9 @@ MAKE_REFLECT_STRUCT(lsMarkedString, language, value);
 
 struct lsTextDocumentContentChangeEvent {
   // The range of the document that changed.
-  lsRange range;
+  optional<lsRange> range;
   // The length of the range that got replaced.
-  int rangeLength = -1;
+  optional<int> rangeLength;
   // The new text of the range/document.
   std::string text;
 };
diff --git a/src/working_files.cc b/src/working_files.cc
index eef15d67..37b68e6c 100644
--- a/src/working_files.cc
+++ b/src/working_files.cc
@@ -324,28 +324,25 @@ void WorkingFiles::OnChange(const lsTextDocumentDidChangeParams& change) {
     return;
   }
 
-  file->version = change.textDocument.version;
+  if (change.textDocument.version)
+    file->version = *change.textDocument.version;
 
   for (const lsTextDocumentContentChangeEvent& diff : change.contentChanges) {
     // Per the spec replace everything if the rangeLength and range are not set.
     // See https://github.com/Microsoft/language-server-protocol/issues/9.
-    if (diff.rangeLength == -1 &&
-        diff.range.start == lsPosition::kZeroPosition &&
-        diff.range.end == lsPosition::kZeroPosition) {
+    if (!diff.range) {
       file->buffer_content = diff.text;
       file->OnBufferContentUpdated();
     } else {
       int start_offset =
-          GetOffsetForPosition(diff.range.start, file->buffer_content);
+          GetOffsetForPosition(diff.range->start, file->buffer_content);
       int end_offset =
-          GetOffsetForPosition(diff.range.end, file->buffer_content);
-      int length = diff.rangeLength;
-      if (length == -1) {
-        length = end_offset - start_offset;
-      }
+          diff.rangeLength
+              ? start_offset + *diff.rangeLength
+              : GetOffsetForPosition(diff.range->end, file->buffer_content);
       file->buffer_content.replace(
           file->buffer_content.begin() + start_offset,
-          file->buffer_content.begin() + start_offset + length, diff.text);
+          file->buffer_content.begin() + end_offset, diff.text);
       file->OnBufferContentUpdated();
     }
   }
diff --git a/src/working_files.h b/src/working_files.h
index 4c82cdab..7089c0be 100644
--- a/src/working_files.h
+++ b/src/working_files.h
@@ -103,4 +103,4 @@ struct WorkingFiles {
   // invalidated if we resize files.
   std::vector<std::unique_ptr<WorkingFile>> files;
   std::mutex files_mutex;  // Protects |files|.
-};
\ No newline at end of file
+};