diff --git a/src/protocol/mod.rs b/src/protocol/mod.rs
index 45f880fbe64dec700ef72086e324877299969e5b..b60caaf6e913262eeb6de01dc0cdc5f74a85aac7 100644
--- a/src/protocol/mod.rs
+++ b/src/protocol/mod.rs
@@ -10,7 +10,7 @@ pub(crate) mod ast_printer;
 use std::sync::Mutex;
 
 use crate::collections::{StringPool, StringRef};
-use crate::protocol::ast::*;
+pub use crate::protocol::ast::*;
 use crate::protocol::eval::*;
 use crate::protocol::input_source::*;
 use crate::protocol::parser::*;
@@ -51,7 +51,7 @@ pub enum ComponentCreationError {
 impl ProtocolDescription {
     pub fn parse(buffer: &[u8]) -> Result<Self, String> {
         let source = InputSource::new(String::new(), Vec::from(buffer));
-        let mut parser = Parser::new();
+        let mut parser = Parser::new()?;
         parser.feed(source).expect("failed to feed source");
         
         if let Err(err) = parser.parse() {
@@ -223,10 +223,10 @@ pub struct ProtocolDescriptionBuilder {
 }
 
 impl ProtocolDescriptionBuilder {
-    pub fn new() -> Self {
-        return Self{
-            parser: Parser::new(),
-        }
+    pub fn new() -> Result<Self, String> {
+        return Ok(Self{
+            parser: Parser::new()?,
+        })
     }
 
     pub fn add(&mut self, filename: String, buffer: Vec<u8>) -> Result<(), ParseError> {