diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/extensions/SimpleGroovyNamedArgumentProvider.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/extensions/SimpleGroovyNamedArgumentProvider.java
index 8cca3ac0e69a..09eb1c437258 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/extensions/SimpleGroovyNamedArgumentProvider.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/extensions/SimpleGroovyNamedArgumentProvider.java
@@ -107,7 +107,7 @@ public class SimpleGroovyNamedArgumentProvider {
           String name = st.nextToken();
 
           Object oldValue = res.put(name, descriptor);
-          assert oldValue == null;
+          assert oldValue == null : "Duplicated attribute name: " + name;
         }
       }