diff --git a/kong/concurrency.lua b/kong/concurrency.lua
index 82bc5ad75fb4..58077d0aeed5 100644
--- a/kong/concurrency.lua
+++ b/kong/concurrency.lua
@@ -1,5 +1,6 @@
 local resty_lock = require "resty.lock"
 local ngx_semaphore = require "ngx.semaphore"
+local in_yieldable_phase = require("kong.tools.utils").in_yieldable_phase
 
 
 local type  = type
@@ -7,9 +8,6 @@ local error = error
 local pcall = pcall
 
 
-local get_phase = ngx.get_phase
-
-
 local concurrency = {}
 
 
@@ -91,7 +89,7 @@ function concurrency.with_coroutine_mutex(opts, fn)
     error("invalid value for opts.on_timeout", 2)
   end
 
-  if get_phase() == "init_worker" then
+  if not in_yieldable_phase() then
     return fn()
   end
 
diff --git a/kong/tools/utils.lua b/kong/tools/utils.lua
index 8b9c3bb9347d..d95a5adcbc85 100644
--- a/kong/tools/utils.lua
+++ b/kong/tools/utils.lua
@@ -1648,26 +1648,45 @@ function _M.sort_by_handler_priority(a, b)
   return prio_a > prio_b
 end
 
-do
+---
+-- Check if the phase is yieldable.
+-- @tparam string phase the phase to check, if not specified then
+-- the default value will be the current phase
+-- @treturn boolean true if the phase is yieldable, false otherwise
+local in_yieldable_phase do
   local get_phase = ngx.get_phase
-  local ngx_sleep = _G.native_ngx_sleep or ngx.sleep
 
-  local SLEEP_PHASES = {
+  -- https://github.com/openresty/lua-nginx-module/blob/c89469e920713d17d703a5f3736c9335edac22bf/src/ngx_http_lua_util.h#L35C10-L35C10
+  local LUA_CONTEXT_YIELDABLE_PHASE = {
     rewrite = true,
+    server_rewrite = true,
     access = true,
     content = true,
     timer = true,
+    ssl_client_hello = true,
     ssl_certificate = true,
     ssl_session_fetch = true,
-    ssl_client_hello = true,
     preread = true,
   }
 
+  in_yieldable_phase = function(phase)
+    if LUA_CONTEXT_YIELDABLE_PHASE[phase or get_phase()] == nil then
+      return false
+    end
+    return true
+  end
+end
+
+_M.in_yieldable_phase = in_yieldable_phase
+
+do
+  local ngx_sleep = _G.native_ngx_sleep or ngx.sleep
+
   local YIELD_ITERATIONS = 1000
   local counter = YIELD_ITERATIONS
 
   function _M.yield(in_loop, phase)
-    if ngx.IS_CLI or SLEEP_PHASES[phase or get_phase()] == nil then
+    if ngx.IS_CLI or not in_yieldable_phase(phase) then
       return
     end
     if in_loop then
diff --git a/spec/02-integration/13-vaults/03-mock_spec.lua b/spec/02-integration/13-vaults/03-mock_spec.lua
index d8e2c896bfa6..77508422afea 100644
--- a/spec/02-integration/13-vaults/03-mock_spec.lua
+++ b/spec/02-integration/13-vaults/03-mock_spec.lua
@@ -145,4 +145,26 @@ for _, strategy in helpers.each_strategy() do
       end)
     end)
   end)
+
+  if strategy == "postgres" then
+    describe("ENV Vault #" .. strategy, function ()
+      describe("Kong Start", function ()
+        it("can resolve reference in init_phase", function ()
+          helpers.setenv("TEST_ENV_VAULT_LOGLEVEL", "debug")
+
+          assert(helpers.start_kong {
+            database = strategy,
+            prefix = helpers.test_conf.prefix,
+            nginx_conf = "spec/fixtures/custom_nginx.template",
+            vaults = "env",
+            log_level = "{vault://env/TEST_ENV_VAULT_LOGLEVEL}"
+          })
+
+          finally(function ()
+            assert(helpers.stop_kong())
+          end)
+        end)
+      end)
+    end)
+  end
 end