diff --git a/t-dll-api.cc b/t-dll-api.cc
index cf3c9b83c..d36bd56f7 100644
--- a/t-dll-api.cc
+++ b/t-dll-api.cc
@@ -354,6 +354,7 @@ extern "C" ivl_expr_t ivl_expr_oper3(ivl_expr_t net)
 
 extern "C" ivl_parameter_t ivl_expr_parameter(ivl_expr_t net)
 {
+      assert(net);
       switch (net->type_) {
 	  case IVL_EX_NUMBER:
 	    return net->u_.number_.parameter;
diff --git a/tgt-stub/statement.c b/tgt-stub/statement.c
index efdb7094d..bf560cf5f 100644
--- a/tgt-stub/statement.c
+++ b/tgt-stub/statement.c
@@ -264,7 +264,12 @@ void show_statement(ivl_statement_t net, unsigned ind)
 		ivl_statement_t f = ivl_stmt_cond_false(net);
 
 		fprintf(out, "%*sif (...)\n", ind, "");
-		show_expression(ex, ind+4);
+		if (ex) {
+		      show_expression(ex, ind+4);
+		} else {
+		      fprintf(out, "%*sERROR: Condition expression is NIL;\n", ind+4, "");
+		      stub_errors += 1;
+		}
 		if (t)
 		      show_statement(t, ind+4);
 		else