diff --git a/src/Scheduler.ts b/src/Scheduler.ts
index 56cbcd6..b7833f2 100644
--- a/src/Scheduler.ts
+++ b/src/Scheduler.ts
@@ -396,10 +396,10 @@ export class Scheduler {
     }
 
     public getIntersection(p: IntersectParams): Availability {
-        const params: AvailabilityParams = <AvailabilityParams> Object.assign(
-            { schedule: null },
-            cloneDeep(omit(p, ['schedules']))
-        );
+        const params: AvailabilityParams = {
+            ...{ schedule: null },
+            ...<AvailabilityParams> cloneDeep(omit(p, ['schedules']))
+        };
         const availabilities: Availability[] = [];
         for (const schedule of p.schedules) {
             params.schedule = schedule;
diff --git a/tsconfig.json b/tsconfig.json
index a6e2475..4ba6c29 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,6 +1,6 @@
 {
   "compilerOptions": {
-    "target": "ES6",
+    "target": "ES5",
     "module": "commonjs",
     "outDir": "./dist/",
     "sourceMap": true,