diff --git a/AstNode.h b/AstNode.h
index 7687e9e..301979c 100644
--- a/AstNode.h
+++ b/AstNode.h
@@ -30,7 +30,7 @@ class Node {
   const yy::location &getLocation() const
   { return location_; }
 
-  virtual void accept(visitor::AstVisitor *visitor) = 0;
+  virtual void accept(visitor::AstVisitor *visitor) const = 0;
 };
 
 }
diff --git a/ast/cxx.py b/ast/cxx.py
index e9a8e5c..173f768 100644
--- a/ast/cxx.py
+++ b/ast/cxx.py
@@ -77,7 +77,7 @@ def end_type(self, name):
     self._print_noncopyable()
     print >> self._deferredOutput
     self._print_getters()
-    print >> self._deferredOutput, '  void accept(visitor::AstVisitor *visitor) override;'
+    print >> self._deferredOutput, '  void accept(visitor::AstVisitor *visitor) const override;'
     print >> self._deferredOutput, '};'
     print >> self._deferredOutput
     print >> self._deferredOutput
diff --git a/ast/cxx_impl.py b/ast/cxx_impl.py
index 3a5607f..982e5ad 100644
--- a/ast/cxx_impl.py
+++ b/ast/cxx_impl.py
@@ -28,7 +28,7 @@ def end_file(self):
     print '}'
 
   def start_type(self, name):
-    print '''void %s::accept(visitor::AstVisitor *visitor) {
+    print '''void %s::accept(visitor::AstVisitor *visitor) const {
   if (visitor->visit%s(*this)) {
 ''' % (name, name)