diff --git a/examples/buildings/building-part-basic.yaml b/examples/buildings/building-part-basic.yaml
index c98ff616..8de4e6b9 100644
--- a/examples/buildings/building-part-basic.yaml
+++ b/examples/buildings/building-part-basic.yaml
@@ -20,6 +20,7 @@ properties:
   version: 1
   level: 1
   updateTime: "2023-06-06T10:30:00-08:00"
+  building: abc123
   height: 21.34
   numFloors: 4
   minHeight: 15.0
diff --git a/schema/buildings/part.yaml b/schema/buildings/part.yaml
index 2e6ee337..daf8d72a 100644
--- a/schema/buildings/part.yaml
+++ b/schema/buildings/part.yaml
@@ -19,6 +19,7 @@ properties:
       - "$ref": ./defs.yaml#/shapeContainer
       - "$ref": ../defs.yaml#/$defs/propertyContainers/overtureFeaturePropertiesContainer
       - "$ref": ../defs.yaml#/$defs/propertyContainers/levelContainer
+    required: [building]
     properties:
       building:
         description: The building ID to which this part belongs