2 files changed, 4 insertions, 0 deletions
diff --git a/diff.h b/diff.h
index cb687436a0..19d762fcd3 100644
--- a/diff.h
+++ b/diff.h
@@ -150,6 +150,7 @@ struct diff_options {
 	diff_format_fn_t format_callback;
 	void *format_callback_data;
 	diff_prefix_fn_t output_prefix;
+	int output_prefix_length;
 	void *output_prefix_data;
 };
 
diff --git a/graph.c b/graph.c
index 7358416a72..7e0a099f83 100644
--- a/graph.c
+++ b/graph.c
@@ -194,8 +194,10 @@ static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void
 	struct git_graph *graph = data;
 	static struct strbuf msgbuf = STRBUF_INIT;
 
+	assert(opt);
 	assert(graph);
 
+	opt->output_prefix_length = graph->width;
 	strbuf_reset(&msgbuf);
 	graph_padding_line(graph, &msgbuf);
 	return &msgbuf;
@@ -245,6 +247,7 @@ struct git_graph *graph_init(struct rev_info *opt)
 	 */
 	opt->diffopt.output_prefix = diff_output_prefix_callback;
 	opt->diffopt.output_prefix_data = graph;
+	opt->diffopt.output_prefix_length = 0;
 
 	return graph;
 }