diff --git a/index.bs b/index.bs
index 267287d..6a4ebb0 100644
--- a/index.bs
+++ b/index.bs
@@ -1105,9 +1105,9 @@ enum WriteCommandType {
 
 dictionary WriteParams {
   required WriteCommandType type;
-  unsigned long long? size;
-  unsigned long long? position;
-  (BufferSource or Blob or USVString)? data;
+  unsigned long long size;
+  unsigned long long position;
+  (BufferSource or Blob or USVString) data;
 };
 
 typedef (BufferSource or Blob or USVString or WriteParams) FileSystemWriteChunkType;