diff --git a/scripts/mbedtls_dev/ecp.py b/scripts/mbedtls_dev/ecp.py
index 93cd212..96ddd05 100644
--- a/scripts/mbedtls_dev/ecp.py
+++ b/scripts/mbedtls_dev/ecp.py
@@ -75,3 +75,86 @@
     @property
     def is_valid(self) -> bool:
         return True
+
+class EcpP521R1Raw(bignum_common.ModOperationCommon,
+                   EcpTarget):
+    """Test cases for ecp quasi_reduction()."""
+    test_function = "ecp_mod_p521_raw"
+    test_name = "ecp_mod_p521_raw"
+    input_style = "fixed"
+    arity = 1
+
+    moduli = [("01ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
+               "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")
+             ] # type: List[str]
+
+    input_values = [
+        "0", "1",
+
+        # Test case for overflow during addition
+        ("0001efffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
+         "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
+         "000001ef"
+         "0000000000000000000000000000000000000000000000000000000000000000"
+         "000000000000000000000000000000000000000000000000000000000f000000"),
+
+        # First 8 number generated by random.getrandbits(1042) - seed(2,2)
+        ("0003cc2e82523e86feac7eb7dc38f519b91751dacdbd47d364be8049a372db8f"
+         "6e405d93ffed9235288bc781ae66267594c9c9500925e4749b575bd13653f8dd"
+         "9b1f282e"
+         "4067c3584ee207f8da94e3e8ab73738fcf1822ffbc6887782b491044d5e34124"
+         "5c6e433715ba2bdd177219d30e7a269fd95bafc8f2a4d27bdcf4bb99f4bea973"),
+        ("00017052829e07b0829a48d422fe99a22c70501e533c91352d3d854e061b9030"
+         "3b08c6e33c7295782d6c797f8f7d9b782a1be9cd8697bbd0e2520e33e44c5055"
+         "6c71c4a6"
+         "6148a86fe8624fab5186ee32ee8d7ee9770348a05d300cb90706a045defc044a"
+         "09325626e6b58de744ab6cce80877b6f71e1f6d2ef8acd128b4f2fc15f3f57eb"),
+        ("00021f15a7a83ee0761ebfd2bd143fa9b714210c665d7435c1066932f4767f26"
+         "294365b2721dea3bf63f23d0dbe53fcafb2147df5ca495fa5a91c89b97eeab64"
+         "ca2ce6bc"
+         "5d3fd983c34c769fe89204e2e8168561867e5e15bc01bfce6a27e0dfcbf87544"
+         "72154e76e4c11ab2fec3f6b32e8d4b8a8f54f8ceacaab39e83844b40ffa9b9f1"),
+        ("000381bc2a838af8d5c44a4eb3172062d08f1bb2531d6460f0caeef038c89b38"
+         "a8acb5137c9260dc74e088a9b9492f258ebdbfe3eb9ac688b9d39cca91551e82"
+         "59cc60b1"
+         "7604e4b4e73695c3e652c71a74667bffe202849da9643a295a9ac6decbd4d3e2"
+         "d4dec9ef83f0be4e80371eb97f81375eecc1cb6347733e847d718d733ff98ff3"),
+        ("00034816c8c69069134bccd3e1cf4f589f8e4ce0af29d115ef24bd625dd961e6"
+         "830b54fa7d28f93435339774bb1e386c4fd5079e681b8f5896838b769da59b74"
+         "a6c3181c"
+         "81e220df848b1df78feb994a81167346d4c0dca8b4c9e755cc9c3adcf515a823"
+         "4da4daeb4f3f87777ad1f45ae9500ec9c5e2486c44a4a8f69dc8db48e86ec9c6"),
+        ("000397846c4454b90f756132e16dce72f18e859835e1f291d322a7353ead4efe"
+         "440e2b4fda9c025a22f1a83185b98f5fc11e60de1b343f52ea748db9e020307a"
+         "aeb6db2c"
+         "3a038a709779ac1f45e9dd320c855fdfa7251af0930cdbd30f0ad2a81b2d19a2"
+         "beaa14a7ff3fe32a30ffc4eed0a7bd04e85bfcdd0227eeb7b9d7d01f5769da05"),
+        ("00002c3296e6bc4d62b47204007ee4fab105d83e85e951862f0981aebc1b00d9"
+         "2838e766ef9b6bf2d037fe2e20b6a8464174e75a5f834da70569c018eb2b5693"
+         "babb7fbb"
+         "0a76c196067cfdcb11457d9cf45e2fa01d7f4275153924800600571fac3a5b26"
+         "3fdf57cd2c0064975c3747465cc36c270e8a35b10828d569c268a20eb78ac332"),
+        ("00009d23b4917fc09f20dbb0dcc93f0e66dfe717c17313394391b6e2e6eacb0f"
+         "0bb7be72bd6d25009aeb7fa0c4169b148d2f527e72daf0a54ef25c0707e33868"
+         "7d1f7157"
+         "5653a45c49390aa51cf5192bbf67da14be11d56ba0b4a2969d8055a9f03f2d71"
+         "581d8e830112ff0f0948eccaf8877acf26c377c13f719726fd70bddacb4deeec"),
+
+        # Next 2 number generated by random.getrandbits(521)
+        ("12b84ae65e920a63ac1f2b64df6dff07870c9d531ae72a47403063238da1a1fe"
+         "3f9d6a179fa50f96cd4aff9261aa92c0e6f17ec940639bc2ccdf572df00790813e3"),
+        ("166049dd332a73fa0b26b75196cf87eb8a09b27ec714307c68c425424a1574f1"
+         "eedf5b0f16cdfdb839424d201e653f53d6883ca1c107ca6e706649889c0c7f38608")
+    ]
+
+    @property
+    def arg_a(self) -> str:
+        return super().format_arg('{:x}'.format(self.int_a)).zfill(2 * self.hex_digits - 2 * self.bits_in_limb // 8)
+
+    def result(self) -> List[str]:
+        result = self.int_a % self.int_n
+        return [self.format_result(result)]
+
+    @property
+    def is_valid(self) -> bool:
+        return True
diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index b9d2b5e..b1a096d 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -4,8 +4,8 @@
 #include "mbedtls/ecdh.h"
 
 #include "bignum_core.h"
-#include "bignum_mod_raw_invasive.h"
 #include "ecp_invasive.h"
+#include "bignum_mod_raw_invasive.h"
 
 #if defined(MBEDTLS_TEST_HOOKS) &&                  \
     (defined(MBEDTLS_ECP_DP_SECP224R1_ENABLED) ||  \
@@ -1344,3 +1344,45 @@
     mbedtls_free(N);
 }
 /* END_CASE */
+
+/* BEGIN_CASE depends_on:MBEDTLS_TEST_HOOKS */
+void ecp_mod_p521_raw(char *input_N,
+                      char *input_X,
+                      char *result)
+{
+    mbedtls_mpi_uint *X = NULL;
+    mbedtls_mpi_uint *N = NULL;
+    mbedtls_mpi_uint *res = NULL;
+    size_t limbs_X;
+    size_t limbs_N;
+    size_t limbs_res;
+
+    mbedtls_mpi_mod_modulus m;
+    mbedtls_mpi_mod_modulus_init(&m);
+
+    TEST_EQUAL(mbedtls_test_read_mpi_core(&X,   &limbs_X,   input_X), 0);
+    TEST_EQUAL(mbedtls_test_read_mpi_core(&N,   &limbs_N,   input_N), 0);
+    TEST_EQUAL(mbedtls_test_read_mpi_core(&res, &limbs_res, result),  0);
+
+    size_t limbs = limbs_N;
+    size_t bytes = limbs * sizeof(mbedtls_mpi_uint);
+
+    TEST_EQUAL(limbs_X, 2 * limbs - 1);
+    TEST_EQUAL(limbs_res, limbs);
+
+    TEST_EQUAL(mbedtls_mpi_mod_modulus_setup(
+                   &m, N, limbs,
+                   MBEDTLS_MPI_MOD_REP_MONTGOMERY), 0);
+
+    TEST_EQUAL(ecp_mod_p521_raw(X, limbs_X), 0);
+    mbedtls_mpi_mod_raw_fix_quasi_reduction(X, &m);
+    ASSERT_COMPARE(X, bytes, res, bytes);
+
+exit:
+    mbedtls_free(X);
+    mbedtls_free(res);
+
+    mbedtls_mpi_mod_modulus_free(&m);
+    mbedtls_free(N);
+}
+/* END_CASE */