add missing const to cast
diff --git a/bn_mp_import.c b/bn_mp_import.c
index 066c5b3..72a4d19 100644
--- a/bn_mp_import.c
+++ b/bn_mp_import.c
@@ -43,7 +43,7 @@ int mp_import(mp_int *rop, size_t count, int order, size_t size,
for (i = 0; i < count; ++i) {
for (j = 0; j < (size - nail_bytes); ++j) {
- unsigned char byte = *((unsigned char *)op +
+ unsigned char byte = *((const unsigned char *)op +
(((order == 1) ? i : ((count - 1u) - i)) * size) +
((endian == 1) ? (j + nail_bytes) : (((size - 1u) - j) - nail_bytes)));