diff --git a/diff.c b/diff.c
index a83409944b..f725d217de 100644
--- a/diff.c
+++ b/diff.c
@@ -5395,7 +5395,6 @@ static int diff_opt_line_prefix(const struct option *opt,
 
 	BUG_ON_OPT_NEG(unset);
 	options->line_prefix = optarg;
-	options->line_prefix_length = strlen(options->line_prefix);
 	graph_setup_line_prefix(options);
 	return 0;
 }
diff --git a/diff.h b/diff.h
index 9901c8ca8c..f816d3b12b 100644
--- a/diff.h
+++ b/diff.h
@@ -274,7 +274,6 @@ struct diff_options {
 	const char *single_follow;
 	const char *a_prefix, *b_prefix;
 	const char *line_prefix;
-	size_t line_prefix_length;
 
 	/**
 	 * collection of boolean options that affects the operation, but some do
diff --git a/graph.c b/graph.c
index 1ca34770ee..34b18a80d4 100644
--- a/graph.c
+++ b/graph.c
@@ -74,10 +74,7 @@ static void graph_show_line_prefix(const struct diff_options *diffopt)
 	if (!diffopt || !diffopt->line_prefix)
 		return;
 
-	fwrite(diffopt->line_prefix,
-	       sizeof(char),
-	       diffopt->line_prefix_length,
-	       diffopt->file);
+	fputs(diffopt->line_prefix, diffopt->file);
 }
 
 static const char **column_colors;
@@ -321,8 +318,7 @@ static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void
 
 	strbuf_reset(&msgbuf);
 	if (opt->line_prefix)
-		strbuf_add(&msgbuf, opt->line_prefix,
-			   opt->line_prefix_length);
+		strbuf_addstr(&msgbuf, opt->line_prefix);
 	if (graph)
 		graph_padding_line(graph, &msgbuf);
 	return &msgbuf;