diff --git a/swig/sentence.i b/swig/sentence.i
index 4d7a14da05e769489c65579f9d8713675f168f53..f639b2f62f476a866ce8f159cf7c109dff394aa8 100644
--- a/swig/sentence.i
+++ b/swig/sentence.i
@@ -43,6 +43,8 @@ namespace Corpus2 {
 
     virtual void append(Token* t);
     const Token* first_token() const;
+
+    const std::string id() const;
   };
 }