diff --git a/src/interpreter.hpp b/src/interpreter.hpp
index 0940ad5..7af5983 100644
--- a/src/interpreter.hpp
+++ b/src/interpreter.hpp
@@ -23,6 +23,7 @@
     void operator()(const delete_&) const;
     void operator()(const ls_&) const;
     void operator()(const discard_&) const;
+    void operator()(const help_&) const;
 
 private:
     template <typename T>