diff --git a/src/encauth/siv/siv.c b/src/encauth/siv/siv.c
index bd6d5b45b..d2e6e1658 100644
--- a/src/encauth/siv/siv.c
+++ b/src/encauth/siv/siv.c
@@ -191,7 +191,8 @@ static int s_siv_S2V(int cipher,
       return err;
    }
 
-   do {
+   /* With zero AD components the loop runs zero times. */
+   while (n < adnum) {
       if (n >= s_siv_max_aad_components) {
          return CRYPT_INPUT_TOO_LONG;
       }
@@ -199,7 +200,7 @@ static int s_siv_S2V(int cipher,
          return err;
       }
       n++;
-   } while(n < adnum);
+   }
 
    return s_siv_S2V_T(&ctx, in, inlen, &D, V);
 }
@@ -470,23 +471,19 @@ int siv_memory(                int  cipher,           int  direction,
       goto err_out;
    }
    va_start(args, adnum);
-   do {
-      if (adnum) {
-         aad = va_arg(args, const unsigned char*);
-         aadlen = va_arg(args, unsigned long);
-      } else {
-         aad = NULL;
-         aadlen = 0;
-      }
+   /* With zero AD components the loop runs zero times. */
+   while (n < adnum) {
       if (n >= s_siv_max_aad_components) {
          err = CRYPT_INPUT_TOO_LONG;
          goto err_out2;
       }
+      aad = va_arg(args, const unsigned char*);
+      aadlen = va_arg(args, unsigned long);
       if ((err = s_siv_S2V_dbl_xor_cmac(&ctx, aad, aadlen, &D)) != CRYPT_OK) {
          goto err_out2;
       }
       n++;
-   } while (n < adnum);
+   }
 
    if ((err = s_siv_S2V_T(&ctx, in_work, in_work_len, &D, &siv.V)) != CRYPT_OK) {
       goto err_out2;
@@ -549,6 +546,13 @@ int siv_test(void)
    unsigned long adlen_A1[] =
       { sizeof(AD_A1), 0 };
 
+   /* Key_A1/Plaintext_A1 with zero AD components */
+   const unsigned char output_A1_noad[] =
+      { 0xf1, 0xc5, 0xfd, 0xea, 0xc1, 0xf1, 0x5a, 0x26,
+        0x77, 0x9c, 0x15, 0x01, 0xf9, 0xfb, 0x75, 0x88,
+        0x27, 0xe9, 0x46, 0xc6, 0x69, 0x08, 0x8a, 0xb0,
+        0x6d, 0xa5, 0x8c, 0x5c, 0x83, 0x1c };
+
    const unsigned char Key_A2[] =
       { 0x7f, 0x7e, 0x7d, 0x7c, 0x7b, 0x7a, 0x79, 0x78,
         0x77, 0x76, 0x75, 0x74, 0x73, 0x72, 0x71, 0x70,
@@ -736,6 +740,36 @@ int siv_test(void)
       return CRYPT_FAIL_TESTVECTOR;
    }
 
+   /* Zero AD components */
+   buflen = sizeof(buf);
+   if ((err = siv_encrypt_memory(cipher, Key_A1, sizeof(Key_A1), 0, NULL, NULL, Plaintext_A1, sizeof(Plaintext_A1), buf, &buflen)) != CRYPT_OK) {
+      return err;
+   }
+   if (ltc_compare_testvector(buf, buflen, output_A1_noad, sizeof(output_A1_noad), "SIV encrypt no AD", 0x5000) != 0) {
+      return CRYPT_FAIL_TESTVECTOR;
+   }
+   buflen = sizeof(buf);
+   if ((err = siv_decrypt_memory(cipher, Key_A1, sizeof(Key_A1), 0, NULL, NULL, output_A1_noad, sizeof(output_A1_noad), buf, &buflen)) != CRYPT_OK) {
+      return err;
+   }
+   if (ltc_compare_testvector(buf, buflen, Plaintext_A1, sizeof(Plaintext_A1), "SIV decrypt no AD", 0x5001) != 0) {
+      return CRYPT_FAIL_TESTVECTOR;
+   }
+   buflen = sizeof(buf);
+   if ((err = siv_memory(cipher, LTC_ENCRYPT, Key_A1, sizeof(Key_A1), Plaintext_A1, sizeof(Plaintext_A1), buf, &buflen, 0, NULL)) != CRYPT_OK) {
+      return err;
+   }
+   if (ltc_compare_testvector(buf, buflen, output_A1_noad, sizeof(output_A1_noad), "siv_memory encrypt no AD", 0x5002) != 0) {
+      return CRYPT_FAIL_TESTVECTOR;
+   }
+   buflen = sizeof(buf);
+   if ((err = siv_memory(cipher, LTC_DECRYPT, Key_A1, sizeof(Key_A1), output_A1_noad, sizeof(output_A1_noad), buf, &buflen, 0, NULL)) != CRYPT_OK) {
+      return err;
+   }
+   if (ltc_compare_testvector(buf, buflen, Plaintext_A1, sizeof(Plaintext_A1), "siv_memory decrypt no AD", 0x5003) != 0) {
+      return CRYPT_FAIL_TESTVECTOR;
+   }
+
    for (n = 0; n < LTC_ARRAY_SIZE(tmp); ++n) {
       tmp[n] = XCALLOC(1, tmpmax);
       if (tmp[n] == NULL) {