diff --git a/bignum.h b/bignum.h
index 5f80ad3af50aed1ece68fe262d6c3522f33875ca..a14f7d6732ecd896634fba26d3ae068cb0c8d0f9 100644
--- a/bignum.h
+++ b/bignum.h
@@ -91,7 +91,7 @@ nettle_mpz_set_sexp(mpz_t x, unsigned limit, struct sexp_iterator *i);
 struct asn1_der_iterator;
 
 int
-asn1_der_get_bignum(struct asn1_der_iterator *iterator,
-		    mpz_t x, unsigned limit);
+nettle_asn1_der_get_bignum(struct asn1_der_iterator *iterator,
+			   mpz_t x, unsigned limit);
 
 #endif /* NETTLE_BIGNUM_H_INCLUDED */