1 files changed, 1 insertions, 1 deletions
diff --git a/luni/src/main/java/libcore/icu/RuleBasedCollatorICU.java b/luni/src/main/java/libcore/icu/RuleBasedCollatorICU.java
index d036c98..4221fe6 100644
--- a/luni/src/main/java/libcore/icu/RuleBasedCollatorICU.java
+++ b/luni/src/main/java/libcore/icu/RuleBasedCollatorICU.java
@@ -46,7 +46,7 @@ public final class RuleBasedCollatorICU implements Cloneable {
 
     public RuleBasedCollatorICU(String rules) throws ParseException {
         if (rules == null) {
-            throw new NullPointerException();
+            throw new NullPointerException("rules == null");
         }
         address = NativeCollation.openCollatorFromRules(rules, VALUE_OFF, VALUE_DEFAULT_STRENGTH);
     }