diff --git a/graph.c b/graph.c
index f8d7a5c0f6d175..e466770208d73d 100644
--- a/graph.c
+++ b/graph.c
@@ -893,7 +893,7 @@ static struct column *find_new_column_by_commit(struct git_graph *graph,
 		if (graph->new_columns[i].commit == commit)
 			return &graph->new_columns[i];
 	}
-	return 0;
+	return NULL;
 }
 
 static void graph_output_post_merge_line(struct git_graph *graph, struct strbuf *sb)