diff --git a/types/jasmine/index.d.ts b/types/jasmine/index.d.ts
index 3259bdb565..c1c15e45de 100644
--- a/types/jasmine/index.d.ts
+++ b/types/jasmine/index.d.ts
@@ -142,7 +142,7 @@ declare namespace jasmine {
     function arrayContaining<T>(sample: ArrayLike<T>): ArrayContaining<T>;
     function arrayWithExactContents<T>(sample: ArrayLike<T>): ArrayContaining<T>;
     function objectContaining<T>(sample: Partial<T>): ObjectContaining<T>;
-    function createSpy(name: string, originalFn?: Function): Spy;
+    function createSpy(name?: string, originalFn?: Function): Spy;
 
     function createSpyObj(baseName: string, methodNames: any[] | {[methodName: string]: any}): any;
     function createSpyObj<T>(baseName: string, methodNames: any[] | {[methodName: string]: any}): SpyObj<T>;