diff --git a/libasn1fix/asn1fix_export.c b/libasn1fix/asn1fix_export.c
index bb598bf..b570925 100644
--- a/libasn1fix/asn1fix_export.c
+++ b/libasn1fix/asn1fix_export.c
@@ -8,7 +8,7 @@
 asn1f_lookup_symbol_ex(
 		asn1p_t *asn,
 		asn1p_expr_t *expr,
-		asn1p_ref_t *ref) {
+		const asn1p_ref_t *ref) {
 	arg_t arg;
 
 	memset(&arg, 0, sizeof(arg));
@@ -28,7 +28,7 @@
 		asn1p_module_t *mod,
 		asn1p_expr_t *expr,
 		asn1p_expr_t *rhs_pspecs,
-		asn1p_ref_t *ref) {
+		const asn1p_ref_t *ref) {
 	arg_t arg;
 
 	memset(&arg, 0, sizeof(arg));