diff --git a/CHANGELOG.md b/CHANGELOG.md
index e42887d..39f73d4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,15 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [5.0.1]
+
+### [Fixed]
+ - An existing bug in constructing a JSON representation for a Pydantic model
+   when the plate_number attribute is 2 or larger resulted in incorrect IDs
+   being generated. The fix includes a return to using Pydantic models' built-in
+   model_dump_json method in order to mitigate the risk that comes with  manual
+   generation of JSON strings.
+
 ## [5.0.0]
 
 ### [Changed]
diff --git a/npg_id_generation/pac_bio.py b/npg_id_generation/pac_bio.py
index 82e3e54..33d2b0c 100644
--- a/npg_id_generation/pac_bio.py
+++ b/npg_id_generation/pac_bio.py
@@ -20,7 +20,6 @@
 # You should have received a copy of the GNU General Public License along with
 # this program. If not, see <http://www.gnu.org/licenses/>.
 
-import io
 import re
 from hashlib import sha256
 from typing import Optional
@@ -57,8 +56,7 @@ class PacBioEntity(BaseModel):
       execution time.
 
       Order the attributes alphabetically to maintain order in the output
-      of model_to_json(). The hash_product_id() method does not depend on
-      the Pydantic ordering, however (it uses a custom JSON serializer).
+      of model_dump_json().
     """
     model_config = ConfigDict(extra="forbid")
 
@@ -112,27 +110,9 @@ def tags_have_correct_characters(cls, v):
     def hash_product_id(self):
         """Generate a sha256sum for the PacBio Entity"""
 
-        # Avoid using Pydantic's model_to_json() method as it requires somewhat
-        # complicated setup with decorators to create our backwards-compatible JSON
-        # serialization.
-
-        # The JSON is built with StringIO to ensure the order of the attributes and
-        # that it's faster than using json.dumps() with sort_keys=True (timeit
-        # estimates that this is ~4x faster.
-        json = io.StringIO()
-        json.write('{"run_name":"')
-        json.write(self.run_name)
-        json.write('","well_label":"')
-        json.write(self.well_label)
-        json.write('"')
         if self.plate_number is not None and self.plate_number > 1:
-            json.write(',"plate_number":')
-            json.write(str(self.plate_number))
-            json.write('"')
-        if self.tags is not None:
-            json.write(',"tags":"')
-            json.write(self.tags)
-            json.write('"')
-        json.write("}")
-
-        return sha256(json.getvalue().encode("utf-8")).hexdigest()
+            json = self.model_dump_json(exclude_none=True)
+        else:
+            json = self.model_dump_json(exclude_none=True, exclude=["plate_number"])
+
+        return sha256(json.encode()).hexdigest()
diff --git a/tests/test_hashing.py b/tests/test_hashing.py
index d579d6d..d5dd486 100644
--- a/tests/test_hashing.py
+++ b/tests/test_hashing.py
@@ -196,14 +196,24 @@ def test_multiple_plates_make_difference():
 def test_expected_hashes():
     """Test against expected hashes."""
     # plate_number absent (historical runs) or plate_number == 1
-    p1_sha256 = "cda15311f706217e31e32d42d524bc35662a6fc15623ce5abe6a31ed741801ae"
+    id1_sha256 = "cda15311f706217e31e32d42d524bc35662a6fc15623ce5abe6a31ed741801ae"
     # plate_number == 2
-    p2_sha256 = "7ca9d350c9b14f0883ac568220b8e5d97148a4eeb41d9de00b5733299d7bcd89"
+    id2_sha256 = "9d883922744395bccb226069cc2b77eac867778e2e31c8c1ac3651ed2a83c059"
+    id3_sha256 = "dc77c4a7f34d84afbb895fcaee72fc8bead9dac20e8d3a9614091d9dd4519acd"
+    id4_sha256 = "e40d98a697a5ffcb09f7ed62597216094198c0d804be100bbb9f6050482182e3"
 
     test_cases = [
-        ('{"run_name": "MARATHON", "well_label": "A1"}', p1_sha256),
-        ('{"run_name": "MARATHON", "well_label": "A1", "plate_number": 1}', p1_sha256),
-        ('{"run_name": "MARATHON", "well_label": "A1", "plate_number": 2}', p2_sha256),
+        ('{"run_name": "MARATHON", "well_label": "A1"}', id1_sha256),
+        ('{"run_name": "MARATHON", "well_label": "A1", "plate_number": 1}', id1_sha256),
+        ('{"run_name": "MARATHON", "well_label": "A1", "plate_number": 2}', id2_sha256),
+        (
+            '{"run_name": "TRACTION_RUN_16", "well_label": "A1", "plate_number": 2}',
+            id3_sha256,
+        ),
+        (
+            '{"run_name": "TRACTION_RUN_16", "well_label": "A1", "plate_number": 3}',
+            id4_sha256,
+        ),
         (
             '{"run_name": "SEMI-MARATHON", "well_label": "D1"}',
             "b55417615e458c23049cc84822531a435c0c4069142f0e1d5e4378d48d9f7bd2",