diff --git a/requirements/test.pip b/requirements/test.pip
index 4e75cf2..8326d0e 100644
--- a/requirements/test.pip
+++ b/requirements/test.pip
@@ -9,5 +9,5 @@ pytest-xdist>=3.0.2
 
 # Pin versions for tests
 matplotlib==3.6.*
-pynrrd==1.0.0
+pynrrd==0.4.3
 seaborn==0.12.*
diff --git a/tests/test_O1_workflow.py b/tests/test_O1_workflow.py
index 7c28b00..fdccdc0 100644
--- a/tests/test_O1_workflow.py
+++ b/tests/test_O1_workflow.py
@@ -50,6 +50,9 @@ def test_ValidateSynthesis(small_O1_working_directory, data_dir):
                 "tolerance": 2e-3,
                 "absolute_tolerance": 1e-15,
             },
+            "synthesis/apical_points.yaml": {
+                "tolerance": 1e-3,
+            },
             "validation/morphology_validation_reports/validation_results.json": {
                 "tolerance": 2e-3,
                 "absolute_tolerance": 1e-12,