diff --git a/PROTOCOL.md b/PROTOCOL.md
index c706bed12df..6327f354b03 100644
--- a/PROTOCOL.md
+++ b/PROTOCOL.md
@@ -1493,12 +1493,12 @@ string | No translation required
 numeric types | The string representation of the number
 date | Encoded as `{year}-{month}-{day}`. For example, `1970-01-01`
 timestamp | Encoded as `{year}-{month}-{day} {hour}:{minute}:{second}` or `{year}-{month}-{day} {hour}:{minute}:{second}.{microsecond}` For example: `1970-01-01 00:00:00`, or `1970-01-01 00:00:00.123456`
-timestamp without timezone | Encoded as `{year}-{month}-{day} {hour}:{minute}:{second}` or `{year}-{month}-{day} {hour}:{minute}:{second}.{microsecond}` For example: `1970-01-01 00:00:00`, or `1970-01-01 00:00:00.123456` To use this type, a table must support a feature `timestampNtz`. See section [Timestamp without timezone (TimestampNTZ)](#timestamp-without-timezone-timestampntz) for more information.
+timestamp_ntz | Encoded as `{year}-{month}-{day} {hour}:{minute}:{second}` or `{year}-{month}-{day} {hour}:{minute}:{second}.{microsecond}` For example: `1970-01-01 00:00:00`, or `1970-01-01 00:00:00.123456` To use this type, a table must support a feature `timestampNtz`. See section [Timestamp without timezone (TimestampNTZ)](#timestamp-without-timezone-timestampntz) for more information.
 boolean | Encoded as the string "true" or "false"
 binary | Encoded as a string of escaped binary values. For example, `"\u0001\u0002\u0003"`
 
 Note: A `timestamp` value in a partition value doesn't store the time zone due to historical reasons.
-It means its behavior looks similar to `timestamp without time zone` when it is used in a partition column.
+It means its behavior looks similar to `timestamp_ntz` when it is used in a partition column.
 
 ## Schema Serialization Format
 
@@ -1521,7 +1521,7 @@ boolean| `true` or `false`
 binary| A sequence of binary data.
 date| A calendar date, represented as a year-month-day triple without a timezone.
 timestamp| Microsecond precision timestamp elapsed since the Unix epoch, 1970-01-01 00:00:00 UTC. When this is stored in a parquet file, its `isAdjustedToUTC` must be set to `true`.
-timestamp without time zone | Microsecond precision timestamp in a local timezone elapsed since the Unix epoch, 1970-01-01 00:00:00. It doesn't have the timezone information, and a value of this type can map to multiple physical time instants. It should always be displayed in the same way, regardless of the local time zone in effect. When this is stored in a parquet file, its `isAdjustedToUTC` must be set to `false`. To use this type, a table must support a feature `timestampNtz`. See section [Timestamp without timezone (TimestampNTZ)](#timestamp-without-timezone-timestampntz) for more information.
+timestamp_ntz| Microsecond precision timestamp in a local timezone elapsed since the Unix epoch, 1970-01-01 00:00:00. It doesn't have the timezone information, and a value of this type can map to multiple physical time instants. It should always be displayed in the same way, regardless of the local time zone in effect. When this is stored in a parquet file, its `isAdjustedToUTC` must be set to `false`. To use this type, a table must support a feature `timestampNtz`. See section [Timestamp without timezone (TimestampNTZ)](#timestamp-without-timezone-timestampntz) for more information.
 
 See Parquet [timestamp type](https://github.com/apache/parquet-format/blob/master/LogicalTypes.md#timestamp) for more details about timestamp and `isAdjustedToUTC`.