diff --git a/src/encauth/siv/siv.c b/src/encauth/siv/siv.c
index bd6d5b45..4de52d90 100644
--- a/src/encauth/siv/siv.c
+++ b/src/encauth/siv/siv.c
@@ -161,7 +161,7 @@ static LTC_INLINE int s_siv_S2V_T(siv_omac_ctx_t *ctx,
    } else {
       s_siv_dbl(D);
       XMEMSET(&T, 0, sizeof(T));
-      XMEMCPY(&T, in, inlen);
+      if (inlen != 0) XMEMCPY(&T, in, inlen);
       T.u.byte[inlen] = 0x80;
       s_siv_xor_buf(D, &T);
 
diff --git a/src/misc/compare_testvector.c b/src/misc/compare_testvector.c
index f1308496..874794ff 100644
--- a/src/misc/compare_testvector.c
+++ b/src/misc/compare_testvector.c
@@ -59,6 +59,8 @@ int ltc_compare_testvector(const void* is, const unsigned long is_len, const voi
    int res = 0;
    if(is_len != should_len) {
       res = is_len > should_len ? -1 : 1;
+   } else if (is_len == 0) {
+      res = 0;
    } else {
       res = XMEMCMP(is, should, is_len);
    }