1 files changed, 1 insertions, 1 deletions
diff --git a/format.h b/format.h
index 3077b739..172f9a85 100644
--- a/format.h
+++ b/format.h
@@ -105,7 +105,7 @@ class format_transaction
   format_transaction(std::ostream&   _output_stream,
 		     const format_t& _first_line_format,
 		     const format_t& _next_lines_format,
-		     const node_t *  display_predicate,
+		     const node_t *  display_predicate = NULL,
 #ifdef COLLAPSED_REGISTER
 		     const bool      _collapsed = false,
 #endif