diff --git a/underscore/underscore.d.ts b/underscore/underscore.d.ts
index a6d48b759..aeaf253ca 100644
--- a/underscore/underscore.d.ts
+++ b/underscore/underscore.d.ts
@@ -180,7 +180,7 @@ interface UnderscoreStatic {
 		context?: any): TResult;
 
 	reduce<T, TResult>(
-		list: _.Collection<T>,
+		list: _.Dictionary<T>,
 		iterator: _.ObjectIterator<T, TResult>,
 		memo?: TResult,
 		context?: any): TResult;