diff --git a/package.json b/package.json
index 34c006ab208..c68c71473c8 100644
--- a/package.json
+++ b/package.json
@@ -127,7 +127,7 @@
     "@types/chai": "4.1.2",
     "@types/lodash": "4.14.102",
     "@types/mocha": "2.2.48",
-    "@types/node": "9.4.5",
+    "@types/node": "^9.4.5",
     "@types/sinon": "4.1.3",
     "@types/sinon-chai": "2.7.29",
     "@types/source-map": "^0.5.2",
diff --git a/src/internal/operators/windowTime.ts b/src/internal/operators/windowTime.ts
index 46c12525768..17ce47e1f32 100644
--- a/src/internal/operators/windowTime.ts
+++ b/src/internal/operators/windowTime.ts
@@ -112,13 +112,13 @@ export function windowTime<T>(windowTimeSpan: number): OperatorFunction<T, Obser
   if (isScheduler(arguments[2])) {
     scheduler = arguments[2];
   } else if (isNumeric(arguments[2])) {
-    maxWindowSize = arguments[2];
+    maxWindowSize = +arguments[2];
   }
 
   if (isScheduler(arguments[1])) {
     scheduler = arguments[1];
   } else if (isNumeric(arguments[1])) {
-    windowCreationInterval = arguments[1];
+    windowCreationInterval = +arguments[1];
   }
 
   return function windowTimeOperatorFunction(source: Observable<T>) {