diff --git a/src/main/java/com/networknt/schema/AdditionalPropertiesValidator.java b/src/main/java/com/networknt/schema/AdditionalPropertiesValidator.java
index 018e60faa..5182bf5ed 100644
--- a/src/main/java/com/networknt/schema/AdditionalPropertiesValidator.java
+++ b/src/main/java/com/networknt/schema/AdditionalPropertiesValidator.java
@@ -108,6 +108,8 @@ public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String
 
     @Override
     public void preloadJsonSchema() {
-        additionalPropertiesSchema.initializeValidators();
+        if(additionalPropertiesSchema!=null) {
+            additionalPropertiesSchema.initializeValidators();
+        }
     }
 }