diff --git a/HISTORY.md b/HISTORY.md
index c45e298..f8e2fdf 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -3,6 +3,12 @@
 https://github.com/josdejong/jsoneditor
 
 
+## not yet released, version 5.2.1
+
+- Fixed #283: improved JSON schema error message in case of no
+  additionalProperties.
+
+
 ## 2016-03-20, version 5.2.0
 
 - Implemented method `editor.destroy()` to properly cleanup the editor (#278).
diff --git a/src/js/util.js b/src/js/util.js
index f760294..c7c8fa7 100644
--- a/src/js/util.js
+++ b/src/js/util.js
@@ -690,6 +690,10 @@ exports.improveSchemaError = function (error) {
     }
   }
 
+  if (error.keyword === 'additionalProperties') {
+    error.message = 'should NOT have additional property: ' + error.params.additionalProperty;
+  }
+
   return error;
 };