diff --git a/test/index.js b/test/index.js
index c2d0fd9..3bcc041 100644
--- a/test/index.js
+++ b/test/index.js
@@ -12,7 +12,7 @@ var forOwn = mout.object.forOwn;
 var gray = colors.gray;
 
 var log = require('./lib/log');
-var JsonFile = require('./lib/JsonFile');
+var PackageOverrideFile = require('./lib/PackageOverrideFile');
 var OverrideFile = require('./lib/OverrideFile');
 var OverridesList = require('./lib/OverridesList');
 
@@ -138,9 +138,9 @@ forOwn(endpoints, function(Endpoint, endpointName){
 		if(program.args.length && program.args.indexOf(fileinfo.canonicalPackageName) === -1 )
 			return;
 
-		var overrideFile = new JsonFile(fileinfo.path);
-		if(overrideFile.hasErrors())
-			return error( util.format('%s is not valid json file \n - %s', gray(fileinfo.path), overrideFile.errors().join('\n -')) );
+		var packageOverrideFile = new PackageOverrideFile(fileinfo.path);
+		if(packageOverrideFile.hasErrors())
+			return error( util.format('%s is not valid package override file \n - %s', gray(fileinfo.path), packageOverrideFile.errors().join('\n -')) );
 
 		ok( fileinfo.canonicalPackageName + '@' + fileinfo.packageVersion );
 	});
diff --git a/test/lib/PackageOverrideFile.js b/test/lib/PackageOverrideFile.js
new file mode 100644
index 0000000..8235418
--- /dev/null
+++ b/test/lib/PackageOverrideFile.js
@@ -0,0 +1,58 @@
+'use strict';
+
+var util = require('util');
+var mout = require('mout');
+var cyan = require('colors/safe').cyan;
+var forEach = mout.array.forEach;
+var isEmpty = mout.lang.isEmpty;
+var deepClone = mout.lang.deepClone;
+var objectUnset = mout.object.unset;
+
+var JsonFile = require('./JsonFile');
+var ALLOWED_PROPERTIES = [
+	'main',
+	'registry',
+	'dependencies',
+	'devDependencies',
+	'directories.lib',
+	'directories.dist',
+	'format',
+	'map',
+	'files',
+	'ignore',
+	'shim',
+
+	'jspmNodeConversion',
+	'browser'
+];
+
+/**
+ * @constructor PackageOverrideFile
+ */
+var PackageOverrideFile = module.exports = function PackageOverrideFile(file){
+
+	if( !(this instanceof PackageOverrideFile) )
+		return new PackageOverrideFile();
+
+	JsonFile.call(this, file);
+
+	if(!this.hasErrors())
+	{
+		var notAllowedProperties = deepClone(this._json);
+
+		forEach(ALLOWED_PROPERTIES, function(allowedProperty){
+
+			objectUnset(notAllowedProperties, allowedProperty);
+
+		});
+
+		if(isEmpty(notAllowedProperties.directories))
+			objectUnset(notAllowedProperties, 'directories');
+
+		if(!isEmpty(notAllowedProperties))
+			this.error( this._file + ' contains not allowed properties: \n\t' + cyan( JSON.stringify(notAllowedProperties) ) );
+	}
+
+};
+
+util.inherits(PackageOverrideFile, JsonFile);
\ No newline at end of file