diff --git a/library/bignum.c b/library/bignum.c
index 60a8df4..0008748 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1102,7 +1102,7 @@
             Z.p[i - t - 1] = ~0;
         else
         {
-#if defined(POLARSSL_HAVE_INT64)
+#if defined(POLARSSL_HAVE_UDBL)
             t_udbl r;
 
             r  = (t_udbl) X.p[i] << biL;