diff --git a/roslib/roslib.d.ts b/roslib/roslib.d.ts
index 9bab4a49f..8610ea7d4 100644
--- a/roslib/roslib.d.ts
+++ b/roslib/roslib.d.ts
@@ -231,7 +231,7 @@ declare module ROSLIB {
 		 * @constructor
 		 * @param values - object matching the fields defined in the .srv definition file
 		 */
-		constructor(values: any);
+		constructor(values?: any);
 	}
 
 	export class ServiceResponse {
@@ -241,7 +241,7 @@ declare module ROSLIB {
 		 * @constructor
 		 * @param values - object matching the fields defined in the .srv definition file
 		 */
-		constructor(values: any);
+		constructor(values?: any);
 	}
 
 	export class Topic {