diff --git a/src/main/java/com/authlete/sd/Disclosure.java b/src/main/java/com/authlete/sd/Disclosure.java
index 55ef981..0fc5380 100644
--- a/src/main/java/com/authlete/sd/Disclosure.java
+++ b/src/main/java/com/authlete/sd/Disclosure.java
@@ -376,6 +376,11 @@ public boolean equals(Object obj)
             return true;
         }
 
+        if (obj == null)
+        {
+            return false;
+        }
+
         if (getClass() != obj.getClass())
         {
             return false;