diff --git a/python/qemu/ot/otp/const.py b/python/qemu/ot/otp/const.py
index ed4b979d2a3f4..3411da8042f35 100644
--- a/python/qemu/ot/otp/const.py
+++ b/python/qemu/ot/otp/const.py
@@ -162,6 +162,10 @@ def load_secrets(self, secrets: dict[str, Any]) -> bool:
             part_size = 0
             part_inv_bytes: list[bytes] = []
             part_inv_sum = 0
+            # there is not a 'buffered' boolean in the HJSON file
+            # the variant is either "unbuffered", "buffered" or "lifecyle";
+            # however lifeycle partition is actually a buffered partition.
+            part_buffered = part.get('variant', '').lower() != 'unbuffered'
             for item in part['items']:
                 size = item['size']
                 name = item['name']
@@ -183,10 +187,16 @@ def load_secrets(self, secrets: dict[str, Any]) -> bool:
             if part_size != part['size']:
                 raise ValueError(f'Invalid byte count for part {part_name}: '
                                  f"{part_size} != {part['size']}")
-            if part_inv_sum:
+            # invalid default values are defined in RTL and HJSON for all
+            # partitions, whereas they can only be used for buffered partitions;
+            # discard values for non-buffered partitions
+            if part_buffered and part_inv_sum:
                 part_inv_str = hexlify(b''.join(part_inv_bytes)).decode()
                 self._inv_defaults.append(part_inv_str)
             else:
+                if part_inv_sum:
+                    self._log.debug('Discard inv default values for unbuffered '
+                                    'part %s', part_name)
                 self._inv_defaults.append(None)
             total_size += part_size
         if total_size != otp_size:
diff --git a/scripts/opentitan/autoreg.py b/scripts/opentitan/autoreg.py
index af91ba97c2b53..33099115c8daf 100755
--- a/scripts/opentitan/autoreg.py
+++ b/scripts/opentitan/autoreg.py
@@ -460,8 +460,8 @@ def _parse_parameters(self, params: list[dict[str, Any]]) \
             -> dict[str, Union[int, bool]]:
         parameters: dict[str, Union[int, bool]] = {}
         converters = {
-            'int': int,
-            'int unsigned': int,
+            'int': HexInt.parse,
+            'int unsigned': HexInt.parse,
             'bit': bool
         }
         for param in params: