diff --git a/src/kyuujitai.test.ts b/src/kyuujitai.test.ts
index 2c49346..3d0ac64 100644
--- a/src/kyuujitai.test.ts
+++ b/src/kyuujitai.test.ts
@@ -9,5 +9,6 @@ describe('kyuujitaiToShinjitai', () => {
     expect(kyuujitaiToShinjitai('隔靴搔痒')).toEqual('隔靴掻痒');
     expect(kyuujitaiToShinjitai('學校')).toEqual('学校');
     expect(kyuujitaiToShinjitai('戶')).toEqual('戸');
+    expect(kyuujitaiToShinjitai('內')).toEqual('内');
   });
 });
diff --git a/src/kyuujitai.ts b/src/kyuujitai.ts
index 966633c..0151c4b 100644
--- a/src/kyuujitai.ts
+++ b/src/kyuujitai.ts
@@ -34,6 +34,7 @@ const KYUU_TO_SHIN: { [c: number]: number } = {
   20745: 20537,
   20818: 20816,
   20841: 20001,
+  20839: 20869,
   20904: 23500,
   20937: 28092,
   20955: 20956,