diff --git a/jssha/jssha-1.6.0.d.ts b/jssha/jssha-1.6.0.d.ts
index 7ff6e2a20..b6dcef80f 100755
--- a/jssha/jssha-1.6.0.d.ts
+++ b/jssha/jssha-1.6.0.d.ts
@@ -6,8 +6,8 @@
 
 declare module jsSHA {
     export interface OutputFormatOptions {
-        outputUpper : boolean;
-        b64Pad : string;
+        outputUpper? : boolean;
+        b64Pad? : string;
     }
 
     export interface jsSHA {