diff --git a/wolfcrypt/src/ecc.c b/wolfcrypt/src/ecc.c
index f7fb835fa..aac9fe657 100644
--- a/wolfcrypt/src/ecc.c
+++ b/wolfcrypt/src/ecc.c
@@ -6299,7 +6299,7 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
     byte *x  = NULL;
     mp_int *z1 = NULL;
 #endif
-    word32 xSz, VSz, KSz, h1len;
+    word32 xSz, VSz, KSz, h1len, qLen;
     byte intOct;
 
     if (hash == NULL || k == NULL || order == NULL) {
@@ -6366,7 +6366,7 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
 #endif
 
     VSz = KSz = hashSz;
-    xSz = h1len = mp_unsigned_bin_size(order);
+    qLen = xSz = h1len = mp_unsigned_bin_size(order);
 
     /* 3.2 b. Set V = 0x01 0x01 ... */
     XMEMSET(V, 0x01, VSz);
@@ -6375,7 +6375,7 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
     XMEMSET(K, 0x00, KSz);
 
     mp_init(z1); /* always init z1 and free z1 */
-    ret = mp_to_unsigned_bin_len(priv, x, xSz);
+    ret = mp_to_unsigned_bin_len(priv, x, qLen);
     if (ret == 0) {
         qbits = mp_count_bits(order);
         ret = mp_read_unsigned_bin(z1, hash, hashSz);
@@ -6440,7 +6440,6 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
 
     /* 3.2 step h. loop through the next steps until a valid value is found */
     if (ret == 0 ) {
-        word32 qLen = (qbits+7)/8;
         int err;
 
         intOct = 0x00;
@@ -6473,10 +6472,10 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
                 ret = mp_read_unsigned_bin(k, x, xSz);
             }
 
-            if ((ret == 0) && ((int)(VSz * WOLFSSL_BIT_SIZE) != qbits)) {
+            if ((ret == 0) && ((int)(xSz * WOLFSSL_BIT_SIZE) != qbits)) {
                 /* handle odd case where shift of 'k' is needed with RFC 6979
                  *  k = bits2int(T) in section 3.2 h.3 */
-                mp_rshb(k, (VSz * WOLFSSL_BIT_SIZE) - qbits);
+                mp_rshb(k, (xSz * WOLFSSL_BIT_SIZE) - qbits);
             }
 
             /* 3.2 step h.3 the key should be smaller than the order of base
diff --git a/wolfcrypt/test/test.c b/wolfcrypt/test/test.c
index 80c8322ef..1e953fd5d 100644
--- a/wolfcrypt/test/test.c
+++ b/wolfcrypt/test/test.c
@@ -20945,6 +20945,85 @@ done:
     wc_ecc_free(&key);
     return ret;
 }
+
+#if defined(HAVE_ECC521)
+/* KAT from RFC6979 */
+static int ecc512_test_deterministic_k(WC_RNG* rng)
+{
+    int ret;
+    ecc_key key;
+    byte sig[ECC_MAX_SIG_SIZE];
+    word32 sigSz;
+    unsigned char msg[] = "sample";
+    unsigned char hash[32];
+
+    const char* dIUT =
+       "0FAD06DAA62BA3B25D2FB40133DA757205DE67F5BB0018FEE8C86E1B68C7E75C"
+       "AA896EB32F1F47C70855836A6D16FCC1466F6D8FBEC67DB89EC0C08B0E996B83"
+       "538";
+    const char* QIUTx =
+        "1894550D0785932E00EAA23B694F213F8C3121F86DC97A04E5A7167DB4E5BCD3"
+        "71123D46E45DB6B5D5370A7F20FB633155D38FFA16D2BD761DCAC474B9A2F502"
+        "3A4";
+    const char* QIUTy =
+        "0493101C962CD4D2FDDF782285E64584139C2F91B47F87FF82354D6630F746A2"
+        "8A0DB25741B5B34A828008B22ACC23F924FAAFBD4D33F81EA66956DFEAA2BFDF"
+        "CF5";
+    const char* expRstr =
+        "1511BB4D675114FE266FC4372B87682BAECC01D3CC62CF2303C92B3526012659"
+        "D16876E25C7C1E57648F23B73564D67F61C6F14D527D54972810421E7D87589E"
+        "1A7";
+    const char* expSstr =
+        "04A171143A83163D6DF460AAF61522695F207A58B95C0644D87E52AA1A347916"
+        "E4F7A72930B1BC06DBE22CE3F58264AFD23704CBB63B29B931F7DE6C9D949A7E"
+        "CFC";
+    mp_int r,s, expR, expS;
+
+    mp_init_multi(&r, &s, &expR, &expS, NULL, NULL);
+    ret = wc_ecc_init_ex(&key, HEAP_HINT, devId);
+    if (ret != 0) {
+        return ret;
+    }
+    ret = wc_ecc_import_raw(&key, QIUTx, QIUTy, dIUT, "SECP521R1");
+    if (ret != 0) {
+        goto done;
+    }
+
+    ret = wc_Hash(WC_HASH_TYPE_SHA256, msg,
+            (word32)XSTRLEN((const char*)msg), hash, sizeof(hash));
+    if (ret != 0) {
+        goto done;
+    }
+
+    ret = wc_ecc_set_deterministic(&key, 1);
+    if (ret != 0) {
+        goto done;
+    }
+
+    sigSz = sizeof(sig);
+    do {
+    #if defined(WOLFSSL_ASYNC_CRYPT)
+        ret = wc_AsyncWait(ret, &key.asyncDev, WC_ASYNC_FLAG_CALL_AGAIN);
+    #endif
+        if (ret == 0)
+            ret = wc_ecc_sign_hash_ex(hash, sizeof(hash), rng, &key, &r, &s);
+    } while (ret == WC_PENDING_E);
+    if (ret != 0) {
+        goto done;
+    }
+    TEST_SLEEP();
+
+    mp_read_radix(&expR, expRstr, MP_RADIX_HEX);
+    mp_read_radix(&expS, expSstr, MP_RADIX_HEX);
+    if (mp_cmp(&r, &expR) != MP_EQ) {
+        ret = -1;
+    }
+
+done:
+    wc_ecc_free(&key);
+    return ret;
+}
+#endif /* HAVE_ECC521 */
 #endif /* WOLFSSL_PUBLIC_MP */
 #endif
 
@@ -23891,6 +23970,13 @@ WOLFSSL_TEST_SUBROUTINE int ecc_test(void)
         printf("ecc384_test_deterministic_k failed! %d\n", ret);
         goto done;
     }
+    #if defined(HAVE_ECC521)
+    ret = ecc512_test_deterministic_k(&rng);
+    if (ret != 0) {
+        printf("ecc512_test_deterministic_k failed! %d\n", ret);
+        goto done;
+    }
+    #endif
     #endif
 #endif