diff --git a/diff.h b/diff.h
index e1e5425..d7edc64 100644
--- a/diff.h
+++ b/diff.h
@@ -194,6 +194,11 @@ struct diff_options {
 	FILE *file;
 	int close_file;
 
+#define OUTPUT_INDICATOR_NEW 0
+#define OUTPUT_INDICATOR_OLD 1
+#define OUTPUT_INDICATOR_CONTEXT 2
+	char output_indicators[3];
+
 	struct pathspec pathspec;
 	pathchange_fn_t pathchange;
 	change_fn_t change;