diff --git a/scripts/mbedtls_dev/ecp.py b/scripts/mbedtls_dev/ecp.py
index bcb6bfb95..93cd2123f 100644
--- a/scripts/mbedtls_dev/ecp.py
+++ b/scripts/mbedtls_dev/ecp.py
@@ -38,6 +38,9 @@ class EcpP192R1Raw(bignum_common.ModOperationCommon,
     input_values = [
         "0", "1",
 
+        # Modulus - 1
+        "fffffffffffffffffffffffffffffffefffffffffffffffe",
+
         # First 8 number generated by random.getrandbits(384) - seed(2,2)
         ("cf1822ffbc6887782b491044d5e341245c6e433715ba2bdd"
          "177219d30e7a269fd95bafc8f2a4d27bdcf4bb99f4bea973"),