diff --git a/src/index.ts b/src/index.ts
index 852eade..b801545 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -35,6 +35,7 @@ const activeMessages: object = reactive({})
  */
 export function isLoaded(lang?: string): boolean {
   lang ??= getActiveLanguage()
+  lang = lang.replace('-', '_')
 
   return loaded.some((row) => row.lang === lang)
 }
@@ -91,7 +92,11 @@ export function transChoice(key: string, number: number, replacements: Replaceme
 /**
  * Translates the given message based on a count and watch for changes.
  */
-export function wTransChoice(key: string, number: number, replacements: ReplacementsInterface = {}): ComputedRef<string> {
+export function wTransChoice(
+  key: string,
+  number: number,
+  replacements: ReplacementsInterface = {}
+): ComputedRef<string> {
   const message = wTrans(key, replacements)
 
   replacements.count = number.toString()
diff --git a/test/translate.test.ts b/test/translate.test.ts
index 4af6bf7..805ee96 100644
--- a/test/translate.test.ts
+++ b/test/translate.test.ts
@@ -90,9 +90,9 @@ it('checks if is a lang is loaded', async () => {
   expect(isLoaded()).toBe(false);
   await global.mountPlugin();
 
-  expect(isLoaded('zh_TW')).toBe(false);
-  await loadLanguageAsync('zh_TW');
-  expect(isLoaded('zh_TW')).toBe(true);
+  expect(isLoaded('zh-TW')).toBe(false);
+  await loadLanguageAsync('zh-TW');
+  expect(isLoaded('zh-TW')).toBe(true);
 })
 
 it('checks if watching translation works', async () => {