diff --git a/lib/resty/healthcheck.lua b/lib/resty/healthcheck.lua
index d7dbf4c8..f754cf9a 100644
--- a/lib/resty/healthcheck.lua
+++ b/lib/resty/healthcheck.lua
@@ -39,6 +39,10 @@ local re_find = ngx.re.find
 local bit = require("bit")
 local ngx_worker_exiting = ngx.worker.exiting
 local ssl = require("ngx.ssl")
+local isarray = require("table.isarray")
+local nkeys = require("table.nkeys")
+local new_tab = require("table.new")
+local escape_uri = ngx.escape_uri
 
 -- constants
 local EVENT_SOURCE_PREFIX = "lua-resty-healthcheck"
@@ -919,8 +923,26 @@ function checker:run_single_check(ip, port, hostname, hostheader)
   end
 
   local req_headers = self.checks.active.headers
-  local headers = table.concat(req_headers, "\r\n")
-  if #headers > 0 then
+  local headers
+  local headers_length = nkeys(req_headers)
+  if headers_length > 0 then
+    if isarray(req_headers) then
+      self:log(WARN, "array headers is deprecated")
+      headers = table.concat(req_headers, "\r\n")
+      return
+    end
+  
+    headers = new_tab(0, headers_length)
+    local idx = 0
+    for k, v in pairs(req_headers) do
+        -- `k` is header name and `v` is header value
+        idx = idx + 1
+        headers[idx] = escape_uri(k) .. ":" .. escape_uri(v)
+    end
+    headers = table.concat(headers, "\r\n")
+  end
+
+  if headers and #headers > 0 then
     headers = headers .. "\r\n"
   end
 
@@ -1271,7 +1293,7 @@ local defaults = {
       http_path = "/",
       https_sni = NO_DEFAULT,
       https_verify_certificate = true,
-      headers = {""},
+      headers = NO_DEFAULT,
       healthy = {
         interval = 0, -- 0 = disabled by default
         http_statuses = { 200, 302 },
@@ -1347,7 +1369,7 @@ end
 -- * `checks.active.http_path`: path to use in `GET` HTTP request to run on active checks
 -- * `checks.active.https_sni`: SNI server name incase of HTTPS
 -- * `checks.active.https_verify_certificate`: boolean indicating whether to verify the HTTPS certificate
--- * `checks.active.hheaders`: an array of headers (no hash-table! must be pre-formatted)
+-- * `checks.active.headers`: one or more lists of values indexed by header name
 -- * `checks.active.healthy.interval`: interval between checks for healthy targets (in seconds)
 -- * `checks.active.healthy.http_statuses`: which HTTP statuses to consider a success
 -- * `checks.active.healthy.successes`: number of successes to consider a target healthy
diff --git a/t/20-req-headers.t b/t/20-req-headers.t
index 304315db..896ca03d 100644
--- a/t/20-req-headers.t
+++ b/t/20-req-headers.t
@@ -15,7 +15,7 @@ run_tests();
 
 __DATA__
 
-=== TEST 1: headers: {"User-Agent", "curl/7.29.0"}
+=== TEST 1: headers: {"User-Agent: curl/7.29.0"}
 --- http_config eval
 qq{
     $::HttpConfig
@@ -65,7 +65,7 @@ Host: 127.0.0.1
 
 
 
-=== TEST 2: headers: {"User-Agent", "curl"}
+=== TEST 2: headers: {"User-Agent: curl"}
 --- http_config eval
 qq{
     $::HttpConfig
@@ -112,3 +112,53 @@ checking healthy targets: #1
 GET /status HTTP/1.0
 User-Agent: curl
 Host: 127.0.0.1
+
+
+
+=== TEST 3: headers: {["User-Agent"] = {"curl"}}
+--- http_config eval
+qq{
+    $::HttpConfig
+
+    server {
+        listen 2112;
+        location = /status {
+            return 200;
+        }
+    }
+}
+--- config
+    location = /t {
+        content_by_lua_block {
+            local we = require "resty.worker.events"
+            assert(we.configure{ shm = "my_worker_events", interval = 0.1 })
+            local healthcheck = require("resty.healthcheck")
+            local checker = healthcheck.new({
+                name = "testing",
+                shm_name = "test_shm",
+                checks = {
+                    active = {
+                        http_path = "/status",
+                        healthy  = {
+                            interval = 0.1
+                        },
+                        headers = { ["User-Agent"] = {"curl"} }
+                    }
+                }
+            })
+            ngx.sleep(0.2) -- wait twice the interval
+            local ok, err = checker:add_target("127.0.0.1", 2112, nil, true)
+            ngx.say(ok)
+            ngx.sleep(0.2) -- wait twice the interval
+        }
+    }
+--- request
+GET /t
+--- response_body
+true
+--- error_log
+checking healthy targets: nothing to do
+checking healthy targets: #1
+GET /status HTTP/1.0
+User-Agent: curl
+Host: 127.0.0.1