diff --git a/test_aodndata/aatams/IMOS_ATF-ACOUSTIC.schema.yaml b/test_aodndata/aatams/IMOS_ATF-ACOUSTIC.schema.yaml
index d4a44bd9..2b67935d 100644
--- a/test_aodndata/aatams/IMOS_ATF-ACOUSTIC.schema.yaml
+++ b/test_aodndata/aatams/IMOS_ATF-ACOUSTIC.schema.yaml
@@ -97,7 +97,6 @@ fields:
     constraints: {'required': True}
   - type: string
     name: transmitter_serial_number
-    constraints: {'required': True}
   - type: integer
     name: transmitter_estimated_battery_life
   - type: string