diff --git a/src/operator/debounceTime.ts b/src/operator/debounceTime.ts
index 529617b758..e718727b46 100644
--- a/src/operator/debounceTime.ts
+++ b/src/operator/debounceTime.ts
@@ -20,7 +20,7 @@ class DebounceTimeOperator<T, R> implements Operator<T, R> {
 
 class DebounceTimeSubscriber<T> extends Subscriber<T> {
   private debouncedSubscription: Subscription<any> = null;
-  private lastValue: any = null;
+  private lastValue: T = null;
 
   constructor(destination: Subscriber<T>,
               private dueTime: number,
@@ -41,7 +41,8 @@ class DebounceTimeSubscriber<T> extends Subscriber<T> {
 
   debouncedNext(): void {
     this.clearDebounce();
-    if (this.lastValue != null) {
+
+    if (this.lastValue !== null) {
       this.destination.next(this.lastValue);
       this.lastValue = null;
     }