diff --git a/diff-no-index.c b/diff-no-index.c
index ce9e783407..e48ab92ba1 100644
--- a/diff-no-index.c
+++ b/diff-no-index.c
@@ -231,8 +231,9 @@ void diff_no_index(struct rev_info *revs,
 
 	if (prefix) {
 		int len = strlen(prefix);
+		const char *paths[3];
+		memset(paths, 0, sizeof(paths));
 
-		revs->diffopt.paths = xcalloc(2, sizeof(char *));
 		for (i = 0; i < 2; i++) {
 			const char *p = argv[argc - 2 + i];
 			/*
@@ -242,12 +243,12 @@ void diff_no_index(struct rev_info *revs,
 			p = (strcmp(p, "-")
 			     ? xstrdup(prefix_filename(prefix, len, p))
 			     : p);
-			revs->diffopt.paths[i] = p;
+			paths[i] = p;
 		}
+		diff_tree_setup_paths(paths, &revs->diffopt);
 	}
 	else
-		revs->diffopt.paths = argv + argc - 2;
-	revs->diffopt.nr_paths = 2;
+		diff_tree_setup_paths(argv + argc - 2, &revs->diffopt);
 	revs->diffopt.skip_stat_unmatch = 1;
 	if (!revs->diffopt.output_format)
 		revs->diffopt.output_format = DIFF_FORMAT_PATCH;