diff --git a/src/transition/transition.ts b/src/transition/transition.ts
index ac7734d5..05b4ca83 100644
--- a/src/transition/transition.ts
+++ b/src/transition/transition.ts
@@ -259,7 +259,9 @@ export class Transition implements IHookRegistry {
    *
    * @returns transition parameter values for the desired path.
    */
-  params(pathname: string = "to"): { [key: string]: any } {
+  params(pathname?: string): any;
+  params<T>(pathname?: string): T;
+  params(pathname: string = "to") {
     return this._treeChanges[pathname].map(prop("paramValues")).reduce(mergeR, {});
   }