diff --git a/lib/actions-impl.js b/lib/actions-impl.js
index fae2039..adfac2b 100644
--- a/lib/actions-impl.js
+++ b/lib/actions-impl.js
@@ -35,6 +35,7 @@ function AbstractAction(Class, props) {
   }
 }
 AbstractAction.prototype = {
+  validate: function validate() { return true; },
   actOnRequest: function unimplementedOnRequest() {
     if (this.unimplemented) { return; }
     throw new Error("Attempted to call unimplemented " +
@@ -55,7 +56,7 @@ var boolActionTpl = [
 var paramActionTpl = [
   "(function() { return function ",
   null,
-  "(param) { this.param = param; }; }());"
+  "(param) { this.param = param; this.validate(); }; }());"
 ];
 function implementAction(action, classProps, instanceProps) {
   var fnTpl = (classProps.type === "bool") ?