--- a/js/src/builtin/AtomicsObject.cpp
+++ b/js/src/builtin/AtomicsObject.cpp
@@ -1024,17 +1024,18 @@ js::FutexRuntime::unlock()
     MOZ_ASSERT(lockHolder_ == PR_GetCurrentThread());
     lockHolder_ = nullptr;
 #endif
     PR_Unlock(lock_);
 }
 
 js::FutexRuntime::FutexRuntime()
   : cond_(nullptr),
-    state_(Idle)
+    state_(Idle),
+    canWait_(false)
 {
 }
 
 bool
 js::FutexRuntime::initInstance()
 {
     MOZ_ASSERT(lock_);
     cond_ = PR_NewCondVar(lock_);