diff --git a/folly/io/async/HHWheelTimer.cpp b/folly/io/async/HHWheelTimer.cpp
index c62fb93df58b4d41dd0e2fd6d5a859ebefc44c4a..65c3fff6e936f078dfbb57a53eda2e6e806c6d5e 100644
--- a/folly/io/async/HHWheelTimer.cpp
+++ b/folly/io/async/HHWheelTimer.cpp
@@ -94,10 +94,12 @@ HHWheelTimer::HHWheelTimer(folly::EventBase* eventBase,
 }
 
 HHWheelTimer::~HHWheelTimer() {
+  CHECK(count_ == 0);
 }
 
 void HHWheelTimer::destroy() {
   assert(count_ == 0);
+  cancelAll();
   DelayedDestruction::destroy();
 }