diff --git a/lib/ast/visitor.js b/lib/ast/visitor.js
index 198b5e1..4148331 100644
--- a/lib/ast/visitor.js
+++ b/lib/ast/visitor.js
@@ -40,7 +40,7 @@ module.exports = {
 };
 
 // Helper's to create visitor's for use with the ASTVisitor class
-const on = ASTVisitor.for = {
+const on = ASTVisitor.on = {
 
     // Visit a node that is defined as a property on another node
     property( name ) {
diff --git a/lib/typings/api.d.ts b/lib/typings/api.d.ts
index b9c4968..f08e728 100644
--- a/lib/typings/api.d.ts
+++ b/lib/typings/api.d.ts
@@ -317,7 +317,15 @@ declare namespace peg {
 
             }
 
+            interface IOn {
+
+                property( name: string ): IVisitor;
+                children( name: string ): IVisitor;
+
+            }
+
             const build: IVisitorBuilder;
+            const on: IFor;
 
         }
 
@@ -325,6 +333,7 @@ declare namespace peg {
 
             ASTVisitor: visitor.ASTVisitor;
             build: visitor.IVisitorBuilder;
+            on: visitor.IOn;
 
         }