diff --git a/xml/src/main/java/org/kxml2/io/KXmlParser.java b/xml/src/main/java/org/kxml2/io/KXmlParser.java
index 2be8d36..80fd8ca 100644
--- a/xml/src/main/java/org/kxml2/io/KXmlParser.java
+++ b/xml/src/main/java/org/kxml2/io/KXmlParser.java
@@ -1612,7 +1612,7 @@
         boolean detectCharset = (charset == null);
 
         if (is == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("is == null");
         }
 
         try {