diff --git a/plyproto/parser.py b/plyproto/parser.py
index 2051c8f..bd35528 100755
--- a/plyproto/parser.py
+++ b/plyproto/parser.py
@@ -357,6 +357,7 @@
         '''message_body_part : field_definition
                            | link_definition
                            | enum_definition
+                           | option_directive
                            | message_definition
                            | extensions_definition
                            | message_extension'''