diff --git a/riverguile.c b/riverguile.c
index b2804ae..aec6592 100644
--- a/riverguile.c
+++ b/riverguile.c
@@ -60,12 +60,11 @@ static void *call_layout_demand_handler (void *data)
 {
 	struct Layout_demand_parameters *params = (struct Layout_demand_parameters *)data;
 
-	SCM call_result = scm_call(
+	SCM call_result = scm_call_3(
 		scm_variable_ref(scm_c_lookup("layout-demand-handler")),
 		scm_from_uint32(params->view_count),
 		scm_from_uint32(params->width),
-		scm_from_uint32(params->height),
-		SCM_UNDEFINED
+		scm_from_uint32(params->height)
 	);
 
 	if ( scm_is_false(scm_list_p(call_result)) == 1 )