diff --git a/scripts/mbedtls_dev/ecp.py b/scripts/mbedtls_dev/ecp.py
index e0fb00035..fa70dedb5 100644
--- a/scripts/mbedtls_dev/ecp.py
+++ b/scripts/mbedtls_dev/ecp.py
@@ -91,6 +91,13 @@ class EcpP521R1Raw(bignum_common.ModOperationCommon,
     input_values = [
         "0", "1",
 
+        # Corner case: maximum canonical P521 multiplication result
+        ("0003ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
+         "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
+         "fffff800"
+         "0000000000000000000000000000000000000000000000000000000000000000"
+         "0000000000000000000000000000000000000000000000000000000000000004"),
+
         # Test case for overflow during addition
         ("0001efffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
          "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"