diff --git a/lib/resty/healthcheck.lua b/lib/resty/healthcheck.lua
index 739301b1..b04b63ef 100644
--- a/lib/resty/healthcheck.lua
+++ b/lib/resty/healthcheck.lua
@@ -1340,7 +1340,7 @@ function _M.new(opts)
   assert(self.shm, ("no shm found by name '%s'"):format(opts.shm_name))
 
   -- other properties
-  self.targets = nil     -- list of targets, initially loaded, maintained by events
+  self.targets = {}     -- list of targets, initially loaded, maintained by events
   self.events = nil      -- hash table with supported events (prevent magic strings)
   self.stopping = true   -- flag to indicate to timers to stop checking
   self.timer_count = 0   -- number of running timers