--- a/src/pt-cmd.h
+++ b/src/pt-cmd.h
@@ -48,12 +48,15 @@
 class tree_if_command;
 class tree_try_catch_command;
 class tree_unwind_protect_command;
+class tree_no_op_command;
 class tree_break_command;
 class tree_continue_command;
 class tree_return_command;
 
 class tree_walker;
 
+#include <string>
+
 #include "pt-base.h"
 
 // A base class for commands.
@@ -290,6 +293,29 @@
   tree_statement_list *catch_code;
 };
 
+// No-op.
+
+class
+tree_no_op_command : public tree_command
+{
+public:
+
+  tree_no_op_command (const string& cmd = "no_op", int l = -1, int c = -1)
+    : tree_command (l, c), orig_cmd (cmd) { }
+
+  ~tree_no_op_command (void) { }
+
+  void eval (void) { }
+
+  void accept (tree_walker& tw);
+
+  string original_command (void) { return orig_cmd; }
+
+private:
+
+  string orig_cmd;
+};
+
 // Break.
 
 class