diff -r 966f32af570d -r 2d96a47a75b1 stage4/generate_c/generate_c_il.cc
--- a/stage4/generate_c/generate_c_il.cc	Wed Oct 24 15:32:48 2012 +0100
+++ b/stage4/generate_c/generate_c_il.cc	Thu Oct 25 11:15:55 2012 +0100
@@ -805,6 +805,7 @@
      * use the IL implicit variable as a source of data to pass to those parameters!
      */
     if ((param_value == NULL) &&  (!used_defvar) && !fp_iterator.is_en_eno_param_implicit()) {
+      if (NULL == implicit_variable_current.datatype) ERROR;
       param_value = &this->implicit_variable_current;
       used_defvar = true;
     }