diff --git a/.luacheckrc b/.luacheckrc
index 1145c0f4..03b9b076 100644
--- a/.luacheckrc
+++ b/.luacheckrc
@@ -13,3 +13,14 @@ not_globals = {
 ignore = {
     "6.", -- ignore whitespace warnings
 }
+
+
+globals = {
+    ngx = {
+        req = {
+            set_uri_args = {
+                read_only = false
+            }
+        }
+    }
+}
diff --git a/lualib/resty/kong/var.lua b/lualib/resty/kong/var.lua
index 2f6685a4..14f12247 100644
--- a/lualib/resty/kong/var.lua
+++ b/lualib/resty/kong/var.lua
@@ -6,6 +6,7 @@ local C = ffi.C
 local ffi_new = ffi.new
 local ffi_str = ffi.string
 local var = ngx.var
+local req = ngx.req
 local type = type
 local error = error
 local assert = assert
@@ -150,6 +151,16 @@ local function var_set_by_index(index, value)
 end
 
 
+local function patch_functions()
+  local orig_set_uri_args = req.set_uri_args
+
+  req.set_uri_args = function(...)
+    variable_index.args = nil
+    return orig_set_uri_args(...)
+  end
+end
+
+
 local function patch_metatable()
     if get_phase() ~= "init" then
         error("patch_metatable can only be called in init phase")
@@ -184,6 +195,8 @@ local function patch_metatable()
 
         return orig_set(self, name, value)
     end
+
+    patch_functions()
 end
 
 
diff --git a/t/005-indexed-var-openresty-suites.t b/t/005-indexed-var-openresty-suites.t
index d34e1b2b..ecc8c78b 100644
--- a/t/005-indexed-var-openresty-suites.t
+++ b/t/005-indexed-var-openresty-suites.t
@@ -9,7 +9,7 @@ use Test::Nginx::Socket::Lua;
 
 repeat_each(2);
 
-plan tests => repeat_each() * (blocks() * 2 + 9 + 4);
+plan tests => repeat_each() * (blocks() * 2 + 9 + 4 + 3);
 
 #no_diff();
 #no_long_string();
@@ -359,3 +359,36 @@ variable not changeable
 ["GET /balancer?port=8091", "GET /balancer?port=8092"]
 --- response_body eval
 ["this is backend peer 8091", "this is backend peer 8092"]
+
+=== TEST 13: patch metatable does not invalidate function req.set_uri_args
+--- http_config
+    lua_package_path "../lua-resty-core/lib/?.lua;lualib/?.lua;;";
+    # this is not required, but set explictly in tests
+    lua_kong_load_var_index $args;
+
+    init_by_lua_block {
+        local var = require "resty.kong.var"
+        var.patch_metatable()
+    }
+
+--- config
+    set $args 'foo=bar';
+
+    location /t {
+        content_by_lua_block {
+            local a = ngx.var.args
+            ngx.req.set_uri_args(a .. "&added=yes")
+            ngx.say(ngx.var.args)
+        }
+    }
+
+--- request
+GET /t
+--- response_body_like
+foo=bar&added=yes
+
+--- error_code: 200
+--- no_error_log
+[error]
+[crit]
+[alert]