thodg/got

diff --git a/lib/diff.c b/lib/diff.c
index 20c62cf..9f91bda 100644
--- a/lib/diff.c
+++ b/lib/diff.c
@@ -125,6 +125,7 @@ got_diff_blob(struct got_blob_object *blob1, struct got_blob_object *blob2,
 	args.label[0] = label1 ? label1 : idstr1;
 	args.label[1] = label2 ? label2 : idstr2;
 	args.diff_context = 3;
+	flags |= D_PROTOTYPE;
 
 	err = got_diffreg(&res, f1, f2, flags, &args, &ds, outfile);
 done: