diff --git a/kong/pdk/private/rate_limiting.lua b/kong/pdk/private/rate_limiting.lua
index 1710372a71df..a267c0a20652 100644
--- a/kong/pdk/private/rate_limiting.lua
+++ b/kong/pdk/private/rate_limiting.lua
@@ -12,6 +12,34 @@ local max_fields_n = 4
 local _M = {}
 
 
+local function _validate_key(key, arg_n, func_name)
+  local typ = type(key)
+  if typ ~= "string" then
+    local msg = string.format(
+      "arg #%d `key` for function `%s` must be a string, got %s",
+      arg_n,
+      func_name,
+      typ
+    )
+    error(msg, 3)
+  end
+end
+
+
+local function _validate_value(value, arg_n, func_name)
+  local typ = type(value)
+  if typ ~= "number" and typ ~= "string" then
+    local msg = string.format(
+      "arg #%d `value` for function `%s` must be a string or a number, got %s",
+      arg_n,
+      func_name,
+      typ
+    )
+    error(msg, 3)
+  end
+end
+
+
 local function _has_rl_ctx(ngx_ctx)
   return ngx_ctx.__rate_limiting_context__ ~= nil
 end
@@ -42,16 +70,8 @@ end
 
 
 function _M.store_response_header(ngx_ctx, key, value)
-  assert(
-    type(key) == "string",
-    "arg #2 `key` for function `store_response_header` must be a string"
-  )
-
-  local value_type = type(value)
-  assert(
-    value_type == "string" or value_type == "number",
-    "arg #3 `value` for function `store_response_header` must be a string or a number"
-  )
+  _validate_key(key, 2, "store_response_header")
+  _validate_value(value, 3, "store_response_header")
 
   local rl_ctx = _get_or_create_rl_ctx(ngx_ctx)
   rl_ctx[key] = value
@@ -59,10 +79,11 @@ end
 
 
 function _M.get_stored_response_header(ngx_ctx, key)
-  assert(
-    type(key) == "string",
-    "arg #2 `key` for function `get_stored_response_header` must be a string"
-  )
+  _validate_key(key, 2, "get_stored_response_header")
+
+  if not _has_rl_ctx(ngx_ctx) then
+    return nil
+  end
 
   if not _has_rl_ctx(ngx_ctx) then
     return nil
diff --git a/t/01-pdk/16-rl-ctx.t b/t/01-pdk/16-rl-ctx.t
index 2c233fd9c01f..66519c9a19c3 100644
--- a/t/01-pdk/16-rl-ctx.t
+++ b/t/01-pdk/16-rl-ctx.t
@@ -140,49 +140,85 @@ X-2: 2
     location = /t {
         rewrite_by_lua_block {
             local pdk_rl = require("kong.pdk.private.rate_limiting")
-            local ok, err
+            local ok, err, errmsg
 
             ok, err = pcall(pdk_rl.store_response_header, ngx.ctx, nil, 1)
             assert(not ok, "pcall should fail")
+            errmsg = string.format(
+                "arg #%d `key` for function `%s` must be a string, got %s",
+                2,
+                "store_response_header",
+                type(nil)
+            )
             assert(
-                err:find("arg #2 `key` for function `store_response_header` must be a string", nil, true),
+                err:find(errmsg, nil, true),
                 "unexpected error message: " .. err
             )
             for _k, v in ipairs({ 1, true, {}, function() end, ngx.null }) do
                 ok, err = pcall(pdk_rl.store_response_header, ngx.ctx, v, 1)
                 assert(not ok, "pcall should fail")
+                errmsg = string.format(
+                    "arg #%d `key` for function `%s` must be a string, got %s",
+                    2,
+                    "store_response_header",
+                    type(v)
+                )
                 assert(
-                    err:find("arg #2 `key` for function `store_response_header` must be a string", nil, true),
+                    err:find(errmsg, nil, true),
                     "unexpected error message: " .. err
                 )
             end
 
             ok, err = pcall(pdk_rl.store_response_header, ngx.ctx, "X-1", nil)
             assert(not ok, "pcall should fail")
+            errmsg = string.format(
+                "arg #%d `value` for function `%s` must be a string or a number, got %s",
+                3,
+                "store_response_header",
+                type(nil)
+            )
             assert(
-                err:find("arg #3 `value` for function `store_response_header` must be a string or a number", nil, true),
+                err:find(errmsg, nil, true),
                 "unexpected error message: " .. err
             )
             for _k, v in ipairs({ true, {}, function() end, ngx.null }) do
                 ok, err = pcall(pdk_rl.store_response_header, ngx.ctx, "X-1", v)
                 assert(not ok, "pcall should fail")
+                errmsg = string.format(
+                    "arg #%d `value` for function `%s` must be a string or a number, got %s",
+                    3,
+                    "store_response_header",
+                    type(v)
+                )
                 assert(
-                    err:find("arg #3 `value` for function `store_response_header` must be a string or a number", nil, true),
+                    err:find(errmsg, nil, true),
                     "unexpected error message: " .. err
                 )
             end
 
             ok, err = pcall(pdk_rl.get_stored_response_header, ngx.ctx, nil)
             assert(not ok, "pcall should fail")
+            errmsg = string.format(
+                "arg #%d `key` for function `%s` must be a string, got %s",
+                2,
+                "get_stored_response_header",
+                type(nil)
+            )
             assert(
-                err:find("arg #2 `key` for function `get_stored_response_header` must be a string", nil, true),
+                err:find(errmsg, nil, true),
                 "unexpected error message: " .. err
             )
             for _k, v in ipairs({ 1, true, {}, function() end, ngx.null }) do
                 ok, err = pcall(pdk_rl.get_stored_response_header, ngx.ctx, v)
                 assert(not ok, "pcall should fail")
+                errmsg = string.format(
+                    "arg #%d `key` for function `%s` must be a string, got %s",
+                    2,
+                    "get_stored_response_header",
+                    type(v)
+                )
                 assert(
-                    err:find("arg #2 `key` for function `get_stored_response_header` must be a string", nil, true),
+                    err:find(errmsg, nil, true),
                     "unexpected error message: " .. err
                 )
             end