Do not directly set Error properties.

Fixes #231

Author: RubenVerborgh

index.js

@@ -597,8 +597,16 @@ function createErrorType(code, message, baseClass) {
 
   // Attach constructor and set default properties
   CustomError.prototype = new (baseClass || Error)();
-  CustomError.prototype.constructor = CustomError;
-  CustomError.prototype.name = "Error [" + code + "]";
+  Object.defineProperties(CustomError.prototype, {
+    constructor: {
+      value: CustomError,
+      enumerable: false,
+    },
+    name: {
+      value: "Error [" + code + "]",
+      enumerable: false,
+    },
+  });
   return CustomError;
 }