diff --git a/src/ast_values.hpp b/src/ast_values.hpp
index f790148..228aac3 100644
--- a/src/ast_values.hpp
+++ b/src/ast_values.hpp
@@ -9,6 +9,7 @@
 
 #include <boost/optional.hpp>
 #include <boost/variant.hpp>
+#include <set>
 
 struct enum_ {
     enum_();
@@ -32,6 +33,12 @@
     bool operator<(const empty_) const;
 };
 
+struct bits_ {
+    bool operator==(const bits_&) const;
+    bool operator<(const bits_&) const;
+    std::set<std::string> m_bits;
+};
+
 struct module_ {
     bool operator==(const module_& b) const;
     bool operator<(const module_& b) const;
@@ -66,6 +73,7 @@
 using leaf_data_ = boost::variant<enum_,
                                   binary_,
                                   empty_,
+                                  bits_,
                                   identityRef_,
                                   special_,
                                   double,