diff --git a/.luacheckrc b/.luacheckrc
index 8981e16a5..207f29ebc 100644
--- a/.luacheckrc
+++ b/.luacheckrc
@@ -1,4 +1,5 @@
 std = 'ngx_lua'
+globals = { 'ngx' }
 unused_args = false
 read_globals = {
     "coroutine._yield"
diff --git a/.travis.yml b/.travis.yml
index 3f5cf76bf..8022909ab 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -37,12 +37,13 @@ env:
     - LD_LIBRARY_PATH=$LUAJIT_LIB:$LD_LIBRARY_PATH
     - TEST_NGINX_SLEEP=0.005
     - TEST_NGINX_RANDOMIZE=1
+    - LUACHECK_VER=0.21.1
   matrix:
     - NGINX_VERSION=1.9.15
     - NGINX_VERSION=1.11.2
 
 before_install:
-  - sudo luarocks install luacheck
+  - sudo luarocks install luacheck $LUACHECK_VER
   - luacheck -q .
   - '! grep -n -P ''(?<=.{80}).+'' --color `find . -name ''*.lua''` || (echo "ERROR: Found Lua source lines exceeding 80 columns." > /dev/stderr; exit 1)'
   - '! grep -n -P ''\t+'' --color `find . -name ''*.lua''` || (echo "ERROR: Cannot use tabs." > /dev/stderr; exit 1)'