--- a/src/parse.y	Tue Mar 17 20:36:01 2009 +0100
+++ b/src/parse.y	Tue May 26 11:20:40 2009 -0400
@@ -3258,6 +3258,12 @@
 
 	  reset_parser ();
 
+	  // Do this with an unwind-protect cleanup function so that
+	  // the forced variables will be unmarked in the event of an
+	  // interrupt. 
+	  symbol_table::scope_id scope = symbol_table::top_scope ();
+	  unwind_protect::add (symbol_table::unmark_forced_variables, &scope);
+
 	  if (! help_txt.empty ())
 	    help_buf.push (help_txt);
 
@@ -3905,10 +3911,19 @@
 
       unwind_protect_ptr (global_command);
 
+      // Do this with an unwind-protect cleanup function so that the
+      // forced variables will be unmarked in the event of an
+      // interrupt.
+      symbol_table::scope_id scope = symbol_table::top_scope ();
+      unwind_protect::add (symbol_table::unmark_forced_variables, &scope);
+
       parse_status = yyparse ();
 
       tree_statement_list *command_list = global_command;
 
+      // Unmark forced variables.
+      unwind_protect::run ();
+
       // Restore previous value of global_command.
       unwind_protect::run ();