--- a/src/pt-const.cc
+++ b/src/pt-const.cc
@@ -2445,6 +2445,13 @@
     }
 }
 
+tree_constant
+tree_constant::eval (int argc, char **argv, int print)
+{
+  ::error ("first element of word-list command is a constant");
+  return tree_constant ();
+}
+
 #if defined (MDEBUG)
 void *
 tree_constant::operator new (size_t size)

--- a/src/pt-const.h
+++ b/src/pt-const.h
@@ -762,6 +762,8 @@
       return retval;
     }
 
+  tree_constant eval (int argc, char **argv, int print);
+
   tree_constant *eval (const tree_constant *args, int n_in, int n_out,
 		       int print)
     { return rep->eval (args, n_in, n_out, print); }