diff --git a/.github/workflows/old_os.yml b/.github/workflows/old_os.yml
deleted file mode 100644
index 9590efc9..00000000
--- a/.github/workflows/old_os.yml
+++ /dev/null
@@ -1,189 +0,0 @@
-name: Build and test for Ubuntu 18.04
-
-on: [push, pull_request]
-
-jobs:
-  build:
-    name: Build and install dependencies
-    runs-on: ubuntu-18.04
-    strategy:
-      matrix:
-        openresty-version: [1.13.6.2, 1.15.8.3, 1.17.8.2, 1.19.9.1]
-        luarocks-version: [3.8.0]
-
-    steps:
-      - name: Update and install OS dependencies
-        run: sudo apt-get update && sudo apt-get install -y libssl-dev ssl-cert
-
-      - name: Set environment variables
-        env:
-          LUAROCKS_VER: ${{ matrix.luarocks-version }}
-          OPENRESTY_VER: ${{ matrix.openresty-version }}
-        run: |
-          echo "DOWNLOAD_PATH=$HOME/download-root" >> $GITHUB_ENV
-          export DOWNLOAD_PATH=$HOME/download-root
-          echo "INSTALL_PATH=$HOME/install-root" >> $GITHUB_ENV
-          export INSTALL_PATH=$HOME/install-root
-          echo "LUAROCKS_VER=$LUAROCKS_VER" >> $GITHUB_ENV
-          echo "OPENRESTY_VER=$OPENRESTY_VER" >> $GITHUB_ENV
-          export LUAROCKS_PREFIX=$INSTALL_PATH/luarocks-$LUAROCKS_VER
-          echo "LUAROCKS_PREFIX=$LUAROCKS_PREFIX" >> $GITHUB_ENV
-          export OPENRESTY_PREFIX=$INSTALL_PATH/openresty-$OPENRESTY_VER
-          echo "OPENRESTY_PREFIX=$OPENRESTY_PREFIX" >> $GITHUB_ENV
-          echo "PATH=$DOWNLOAD_PATH:$LUAROCKS_PREFIX/bin:$OPENRESTY_PREFIX/nginx/sbin:$DOWNLOAD_PATH/cpanm:$PATH" >> $GITHUB_ENV
-
-      - name: Checkout lua-resty-healthcheck
-        uses: actions/checkout@v2
-
-      - name: Lookup build cache
-        uses: actions/cache@v2
-        id: cache-deps
-        with:
-          path: |
-            ${{ env.INSTALL_PATH }}
-            ~/perl5
-          key: ${{ runner.os }}-${{ matrix.openresty-version }}-${{ hashFiles('.github/workflows/old_os.yml') }}
-
-      - name: Create needed paths
-        if: steps.cache-deps.outputs.cache-hit != 'true'
-        run: |
-          mkdir -p $DOWNLOAD_PATH
-          mkdir -p $INSTALL_PATH
-
-      - name: Build and install OpenResty ${{ matrix.openresty-version }}
-        if: steps.cache-deps.outputs.cache-hit != 'true'
-        run: |
-          if [ ! -d $INSTALL_PATH/openresty-$OPENRESTY_VER ];
-          then
-            pushd $DOWNLOAD_PATH
-            echo "Downloading from http://openresty.org/download/openresty-$OPENRESTY_VER.tar.gz"
-            wget -O $DOWNLOAD_PATH/openresty-$OPENRESTY_VER.tar.gz http://openresty.org/download/openresty-$OPENRESTY_VER.tar.gz
-            echo "tar -zxf $DOWNLOAD_PATH/openresty-$OPENRESTY_VER.tar.gz"
-            tar -zxf $DOWNLOAD_PATH/openresty-$OPENRESTY_VER.tar.gz
-            echo "result: $?"
-            pushd openresty-$OPENRESTY_VER
-            ./configure --prefix=$OPENRESTY_PREFIX
-            make
-            make install
-            popd
-            popd
-          fi
-
-      - name: Build and install LuaRocks ${{ matrix.luarocks-version }}
-        if: steps.cache-deps.outputs.cache-hit != 'true'
-        run: |
-          if [ ! -d $INSTALL_PATH/luarocks-$LUAROCKS_VER ];
-          then
-            pushd $DOWNLOAD_PATH
-            echo "Downloading from https://luarocks.github.io/luarocks/releases/luarocks-$LUAROCKS_VER.tar.gz"
-            wget -O $DOWNLOAD_PATH/luarocks-$LUAROCKS_VER.tar.gz https://luarocks.github.io/luarocks/releases/luarocks-$LUAROCKS_VER.tar.gz
-            tar -zxf $DOWNLOAD_PATH/luarocks-$LUAROCKS_VER.tar.gz
-            pushd luarocks-$LUAROCKS_VER
-            ./configure --prefix=$LUAROCKS_PREFIX --with-lua=$OPENRESTY_PREFIX/luajit --with-lua-include=$OPENRESTY_PREFIX/luajit/include/luajit-2.1 --lua-suffix=jit
-            make build
-            make install
-            popd
-            luarocks install luacheck
-            popd
-          fi
-
-      - name: Install Test::NGINX
-        if: steps.cache-deps.outputs.cache-hit != 'true'
-        run: |
-          if [ ! -f $DOWNLOAD_PATH/cpanm ];
-          then
-            wget -O $DOWNLOAD_PATH/cpanm https://cpanmin.us/
-            chmod +x $DOWNLOAD_PATH/cpanm
-            cpanm --notest --local-lib=$HOME/perl5 local::lib && eval $(perl -I $HOME/perl5/lib/perl5/ -Mlocal::lib)
-            cpanm --notest Test::Nginx
-          fi
-
-  lint:
-    name: Static code analysis
-    runs-on: ubuntu-18.04
-    needs: build
-    strategy:
-      matrix:
-        openresty-version: [1.13.6.2, 1.15.8.3, 1.17.8.2, 1.19.9.1]
-        luarocks-version: [3.8.0]
-    steps:
-      - name: Checkout lua-resty-healthcheck
-        uses: actions/checkout@v2
-
-      - name: Set environment variables
-        env:
-          LUAROCKS_VER: ${{ matrix.luarocks-version }}
-          OPENRESTY_VER: ${{ matrix.openresty-version }}
-        run: |
-          echo "DOWNLOAD_PATH=$HOME/download-root" >> $GITHUB_ENV
-          export DOWNLOAD_PATH=$HOME/download-root
-          echo "INSTALL_PATH=$HOME/install-root" >> $GITHUB_ENV
-          export INSTALL_PATH=$HOME/install-root
-          echo "LUAROCKS_VER=$LUAROCKS_VER" >> $GITHUB_ENV
-          echo "OPENRESTY_VER=$OPENRESTY_VER" >> $GITHUB_ENV
-          export LUAROCKS_PREFIX=$INSTALL_PATH/luarocks-$LUAROCKS_VER
-          echo "LUAROCKS_PREFIX=$LUAROCKS_PREFIX" >> $GITHUB_ENV
-          export OPENRESTY_PREFIX=$INSTALL_PATH/openresty-$OPENRESTY_VER
-          echo "OPENRESTY_PREFIX=$OPENRESTY_PREFIX" >> $GITHUB_ENV
-          echo "PATH=$DOWNLOAD_PATH:$LUAROCKS_PREFIX/bin:$OPENRESTY_PREFIX/nginx/sbin:$DOWNLOAD_PATH/cpanm:$PATH" >> $GITHUB_ENV
-
-      - name: Lookup build cache
-        uses: actions/cache@v2
-        id: cache-deps
-        with:
-          path: |
-            ${{ env.INSTALL_PATH }}
-            ~/perl5
-          key: ${{ runner.os }}-${{ matrix.openresty-version }}-${{ hashFiles('.github/workflows/old_os.yml') }}
-
-      - name: Lint code
-        run: |
-          eval `luarocks path`
-          luacheck lib
-
-  install-and-test:
-    name: Test lua-resty-healthcheck
-    runs-on: ubuntu-18.04
-    needs: build
-    strategy:
-      matrix:
-        openresty-version: [1.13.6.2, 1.15.8.3, 1.17.8.2, 1.19.9.1]
-        luarocks-version: [3.8.0]
-    steps:
-      - name: Checkout lua-resty-healthcheck
-        uses: actions/checkout@v2
-
-      - name: Set environment variables
-        env:
-          LUAROCKS_VER: ${{ matrix.luarocks-version }}
-          OPENRESTY_VER: ${{ matrix.openresty-version }}
-        run: |
-          echo "DOWNLOAD_PATH=$HOME/download-root" >> $GITHUB_ENV
-          export DOWNLOAD_PATH=$HOME/download-root
-          echo "INSTALL_PATH=$HOME/install-root" >> $GITHUB_ENV
-          export INSTALL_PATH=$HOME/install-root
-          echo "LUAROCKS_VER=$LUAROCKS_VER" >> $GITHUB_ENV
-          echo "OPENRESTY_VER=$OPENRESTY_VER" >> $GITHUB_ENV
-          export LUAROCKS_PREFIX=$INSTALL_PATH/luarocks-$LUAROCKS_VER
-          echo "LUAROCKS_PREFIX=$LUAROCKS_PREFIX" >> $GITHUB_ENV
-          export OPENRESTY_PREFIX=$INSTALL_PATH/openresty-$OPENRESTY_VER
-          echo "OPENRESTY_PREFIX=$OPENRESTY_PREFIX" >> $GITHUB_ENV
-          echo "PATH=$DOWNLOAD_PATH:$LUAROCKS_PREFIX/bin:$OPENRESTY_PREFIX/nginx/sbin:$DOWNLOAD_PATH/cpanm:$PATH" >> $GITHUB_ENV
-
-      - name: Lookup build cache
-        uses: actions/cache@v2
-        id: cache-deps
-        with:
-          path: |
-            ${{ env.INSTALL_PATH }}
-            ~/perl5
-          key: ${{ runner.os }}-${{ matrix.openresty-version }}-${{ hashFiles('.github/workflows/old_os.yml') }}
-
-      - name: Install lua-resty-healthcheck
-        run: luarocks make
-
-      - name: Run tests
-        run: |
-          eval `luarocks path`
-          eval $(perl -I $HOME/perl5/lib/perl5/ -Mlocal::lib)
-          TEST_NGINX_RANDOMIZE=1 prove -I. -r t
diff --git a/lib/resty/healthcheck.lua b/lib/resty/healthcheck.lua
index 3922d582..58304aa2 100644
--- a/lib/resty/healthcheck.lua
+++ b/lib/resty/healthcheck.lua
@@ -1650,11 +1650,13 @@ function _M.new(opts)
         end
 
         local cur_time = ngx_now()
+        local is_checked = false
         for _, checker_obj in pairs(hcs) do
 
           if (last_cleanup_check + CLEANUP_INTERVAL) < cur_time then
             -- clear targets marked for delayed removal
             locking_target_list(checker_obj, function(target_list)
+              is_checked = true
               local removed_targets = {}
               local index = 1
               while index <= #target_list do
@@ -1681,8 +1683,6 @@ function _M.new(opts)
                 end
               end
             end)
-
-            last_cleanup_check = cur_time
           end
 
           if checker_obj.checks.active.healthy.active and
@@ -1701,6 +1701,9 @@ function _M.new(opts)
             checker_callback(checker_obj, "unhealthy")
           end
         end
+        if is_checked then
+          last_cleanup_check = cur_time
+        end
       end,
     })
     if not active_check_timer then
diff --git a/t/11-clear.t b/t/11-clear.t
index 0ddb02d5..dabafc09 100644
--- a/t/11-clear.t
+++ b/t/11-clear.t
@@ -3,7 +3,7 @@ use Cwd qw(cwd);
 
 workers(1);
 
-plan tests => repeat_each() * 27;
+plan tests => repeat_each() * 27 + 2;
 
 my $pwd = cwd();
 
@@ -280,3 +280,86 @@ false
 target not found
 false
 target not found
+
+
+=== TEST 6: delayed_clear() would clear tgt list when we add two checkers
+--- http_config eval: $::HttpConfig
+--- 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 config1 = {
+                name = "testing",
+                shm_name = "test_shm",
+                checks = {
+                    active = {
+                        healthy  = {
+                            interval = 0.1
+                        },
+                        unhealthy  = {
+                            interval = 0.1
+                        }
+                    }
+                }
+            }
+
+            local config2 = {
+                name = "testing2",
+                shm_name = "test_shm",
+                checks = {
+                    active = {
+                        healthy  = {
+                            interval = 0.1
+                        },
+                        unhealthy  = {
+                            interval = 0.1
+                        }
+                    }
+                }
+            }
+
+            local checker1 = healthcheck.new(config1)
+            checker1:add_target("127.0.0.1", 10001, nil, true)
+            checker1:add_target("127.0.0.1", 10002, nil, true)
+            checker1:add_target("127.0.0.1", 10003, nil, true)
+            ngx.say(checker1:get_target_status("127.0.0.1", 10002))
+            checker1:delayed_clear(0.2)
+
+            local checker2 = healthcheck.new(config2)
+            checker2:add_target("127.0.0.1", 10001, nil, true)
+            checker2:add_target("127.0.0.1", 10002, nil, true)
+            ngx.say(checker2:get_target_status("127.0.0.1", 10002))
+            checker2:delayed_clear(0.2)
+
+            ngx.sleep(3) -- wait twice the interval
+
+            local status, err = checker1:get_target_status("127.0.0.1", 10001)
+            if status ~= nil then
+                ngx.say(status)
+            else
+                ngx.say(err)
+            end
+            status, err = checker2:get_target_status("127.0.0.1", 10002)
+            if status ~= nil then
+                ngx.say(status)
+            else
+                ngx.say(err)
+            end
+            status, err = checker2:get_target_status("127.0.0.1", 10003)
+            if status ~= nil then
+                ngx.say(status)
+            else
+                ngx.say(err)
+            end
+        }
+    }
+--- request
+GET /t
+--- response_body
+true
+true
+target not found
+target not found
+target not found