diff --git a/handlebars/handlebars.d.ts b/handlebars/handlebars.d.ts
index aa5e72086..f6b0c5565 100644
--- a/handlebars/handlebars.d.ts
+++ b/handlebars/handlebars.d.ts
@@ -5,7 +5,7 @@
 
 
 interface HandlebarsStatic {
-    registerHelper(name: string, fn: Function, inverse?: bool): void;
+    registerHelper(name: string, fn: Function, inverse?: boolean): void;
     registerPartial(name: string, str): void;
     K();
     createFrame(object);
@@ -20,4 +20,4 @@ interface HandlebarsStatic {
     compile(environment, options?, context?, asObject?);
 }
 
-declare var Handlebars: HandlebarsStatic;
\ No newline at end of file
+declare var Handlebars: HandlebarsStatic;