diff --git a/src/lib/consts.ts b/src/lib/consts.ts
index cb479e3..eb0919c 100644
--- a/src/lib/consts.ts
+++ b/src/lib/consts.ts
@@ -1,5 +1,6 @@
 export const REQUEST_ID_HEADER = 'x-request-id';
 export const REQUEST_ID_PARAM_NAME = 'requestId';
 export const USER_ID_PARAM_NAME = 'userId';
+export const USER_LANGUAGE_PARAM_NAME = 'userLang';
 export const TRACE_KEY = 'uber-trace-id';
 export const REDACTED_STRING = '[REDACTED]';
diff --git a/src/types.ts b/src/types.ts
index 44c2213..672d5c7 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,6 +1,6 @@
 import type {pino} from 'pino';
 
-import {REQUEST_ID_PARAM_NAME, USER_ID_PARAM_NAME} from './lib/consts';
+import {REQUEST_ID_PARAM_NAME, USER_ID_PARAM_NAME, USER_LANGUAGE_PARAM_NAME} from './lib/consts';
 import type {LoggingLevel} from './lib/logging';
 
 export interface AppConfig {
@@ -47,6 +47,7 @@ export interface AppConfig {
 export interface AppContextParams {
     [REQUEST_ID_PARAM_NAME]?: string;
     [USER_ID_PARAM_NAME]?: string;
+    [USER_LANGUAGE_PARAM_NAME]?: string;
 }
 
 export interface AppDynamicConfig {}