diff --git a/tests/suites/test_suite_psa_crypto.data b/tests/suites/test_suite_psa_crypto.data
index a5fb4c712b..db3824078a 100644
--- a/tests/suites/test_suite_psa_crypto.data
+++ b/tests/suites/test_suite_psa_crypto.data
@@ -7294,6 +7294,83 @@ PSA (raw) key agreement: X25519 (RFC 7748: Bob)
 depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
 key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a":"4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742":PSA_SUCCESS
 
+# RFC 7748 says we need clip the input to 255 bits, see decodeUCoordinate().
+# Check we indeed do that: same inputs as above except bit 256 is set in the
+# peer's public key (little endian, so that's the MSB of the last byte).
+PSA (raw) key agreement: X25519 (RFC 7748: Alice with bit 256 set)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a":"de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882bcf":"4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742":PSA_SUCCESS
+
+PSA (raw) key agreement: X25519 (RFC 7748: Bob with bit 256 set)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4eea":"4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742":PSA_SUCCESS
+
+# BEGIN list from https://cr.yp.to/ecdh.html#validate
+PSA (raw) key agreement: X25519 (peer key is 0)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"0000000000000000000000000000000000000000000000000000000000000000":"":PSA_ERROR_INVALID_ARGUMENT
+
+PSA (raw) key agreement: X25519 (peer key is 1)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"0100000000000000000000000000000000000000000000000000000000000000":"":PSA_ERROR_INVALID_ARGUMENT
+
+# this is x25519_bad_point_1 in ecp.c
+PSA (raw) key agreement: X25519 (peer key is bad_point_1)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"e0eb7a7c3b41b8ae1656e3faf19fc46ada098deb9c32b1fd866205165f49b800":"":PSA_ERROR_INVALID_ARGUMENT
+
+# this is x25519_bad_point_2 in ecp.c
+PSA (raw) key agreement: X25519 (peer key is bad_point_2)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"5f9c95bca3508c24b1d0b1559c83ef5b04445cc4581c8e86d8224eddd09f1157":"":PSA_ERROR_INVALID_ARGUMENT
+
+PSA (raw) key agreement: X25519 (peer key is p-1)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"ecffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f":"":PSA_ERROR_INVALID_ARGUMENT
+
+PSA (raw) key agreement: X25519 (peer key is p)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"edffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f":"":PSA_ERROR_INVALID_ARGUMENT
+
+PSA (raw) key agreement: X25519 (peer key is p+1)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"eeffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f":"":PSA_ERROR_INVALID_ARGUMENT
+# END list from https://cr.yp.to/ecdh.html#validate
+# Further values in that list are larger that 2^256, and per RFC 7748
+# we clip the input to 255 bits, that is, set bit 256 to zero.
+# So, what's actually useful to test is 2^256 + x (aka x | (1 << 256))
+# where x is any of the values above. (Reminder: little-endian.)
+
+PSA (raw) key agreement: X25519 (peer key is 2^256 + 0)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"0000000000000000000000000000000000000000000000000000000000000080":"":PSA_ERROR_INVALID_ARGUMENT
+
+PSA (raw) key agreement: X25519 (peer key is 2^256 + 1)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"0100000000000000000000000000000000000000000000000000000000000080":"":PSA_ERROR_INVALID_ARGUMENT
+
+# this is x25519_bad_point_1 in ecp.c
+PSA (raw) key agreement: X25519 (peer key is 2^256 + bad_point_1)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"e0eb7a7c3b41b8ae1656e3faf19fc46ada098deb9c32b1fd866205165f49b880":"":PSA_ERROR_INVALID_ARGUMENT
+
+# this is x25519_bad_point_2 in ecp.c
+PSA (raw) key agreement: X25519 (peer key is 2^256 + bad_point_2)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"5f9c95bca3508c24b1d0b1559c83ef5b04445cc4581c8e86d8224eddd09f11d7":"":PSA_ERROR_INVALID_ARGUMENT
+
+PSA (raw) key agreement: X25519 (peer key is 2^256 + p-1)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"ecffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff":"":PSA_ERROR_INVALID_ARGUMENT
+
+PSA (raw) key agreement: X25519 (peer key is 2^256 + p)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"edffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff":"":PSA_ERROR_INVALID_ARGUMENT
+
+PSA (raw) key agreement: X25519 (peer key is 2^256 + p+1)
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255
+key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"eeffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff":"":PSA_ERROR_INVALID_ARGUMENT
+
 # see generating script in commit message
 PSA (raw) key agreement: X25519 (shared secret with MSB 0)
 depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255