diff --git a/data_steward/resource_files/schemas/cdm/clinical/person.json b/data_steward/resource_files/schemas/cdm/clinical/person.json
index b011337935..09fe0c2673 100644
--- a/data_steward/resource_files/schemas/cdm/clinical/person.json
+++ b/data_steward/resource_files/schemas/cdm/clinical/person.json
@@ -14,7 +14,7 @@
   {
     "type": "integer",
     "name": "year_of_birth",
-    "mode": "required",
+    "mode": "nullable",
     "description": "The year of birth of the person. For data sources with date of birth, the year is extracted. For data sources where the year of birth is not available, the approximate year of birth is derived based on any age group categorization available."
   },
   {