diff --git a/tutorial/tutorial.thrift b/tutorial/tutorial.thrift
index 6e83939..bc199e4 100755
--- a/tutorial/tutorial.thrift
+++ b/tutorial/tutorial.thrift
@@ -78,11 +78,16 @@
  * Structs are the basic complex data structures. They are comprised of fields
  * which each have an integer identifier, a type, a symbolic name, and an
  * optional default value.
+ *
+ * Fields can be declared "optional", which ensures they will not be included
+ * in the serialized output if they aren't set.  Note that this requires some
+ * manual management in some languages.
  */
 struct Work {
   1: i32 num1 = 0,
   2: i32 num2,
-  3: Operation op
+  3: Operation op,
+  4: optional string comment,
 }
 
 /**