diff --git a/src/encauth/siv/siv.c b/src/encauth/siv/siv.c
index bd6d5b45b..4de52d90b 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 f13084960..fd8ae0c77 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 && (!is || !should)) {
+      res = 0;
    } else {
       res = XMEMCMP(is, should, is_len);
    }
diff --git a/src/pk/ec25519/tweetnacl.c b/src/pk/ec25519/tweetnacl.c
index 48446ef9a..4fee24064 100644
--- a/src/pk/ec25519/tweetnacl.c
+++ b/src/pk/ec25519/tweetnacl.c
@@ -53,7 +53,7 @@ sv car25519(gf o)
     o[i]+=(1LL<<16);
     c=o[i]>>16;
     o[(i+1)*(i<15)]+=c-1+37*(c-1)*(i==15);
-    o[i]-=c<<16;
+    o[i]-=((i64)(((u64)(c))<<16));
   }
 }
 
@@ -366,7 +366,7 @@ sv modL(u8 *r,i64 x[64])
     for (j = i - 32;j < i - 12;++j) {
       x[j] += carry - 16 * x[i] * L[j - (i - 32)];
       carry = (x[j] + 128) >> 8;
-      x[j] -= carry << 8;
+      x[j] -= ((i64)(((u64)(carry)) << 8));
     }
     x[j] += carry;
     x[i] = 0;
diff --git a/src/pk/ec448/ec448_common.c b/src/pk/ec448/ec448_common.c
index 65bb0f2bb..c8cb71600 100644
--- a/src/pk/ec448/ec448_common.c
+++ b/src/pk/ec448/ec448_common.c
@@ -96,13 +96,13 @@ static void s_gf448_carry(gf448 o)
    for (i = 0; i < 15; ++i) {
       c = o[i] >> 28;
       o[i+1] += c;
-      o[i] -= c << 28;
+      o[i] -= ((long64)(((ulong64)(c)) << 28));
    }
    /* limb 15 overflow: 2^(28*16) = 2^448 == 2^224 + 1 */
    c = o[15] >> 28;
    o[0]  += c;     /* + c * 1 */
    o[8]  += c;     /* + c * 2^224 */
-   o[15] -= c << 28;
+   o[15] -= ((long64)(((ulong64)(c)) << 28));
    /* one more pass to settle the extra from limb 0 and 8 */
    for (i = 0; i < 15; ++i) {
       c = o[i] >> 28;
@@ -254,7 +254,7 @@ static void s_gf448_mul(gf448 o, const gf448 a, const gf448 b)
    for (i = 0; i < 30; ++i) {
       c = t[i] >> 28;
       t[i+1] += c;
-      t[i] -= c << 28;
+      t[i] -= ((long64)(((ulong64)(c)) << 28));
    }
    t[14] += 2 * t[30];
    t[6]  += t[30];