diff --git a/db/db-core/src/lib.rs b/db/db-core/src/lib.rs
index 163f6445..ef33a7ac 100644
--- a/db/db-core/src/lib.rs
+++ b/db/db-core/src/lib.rs
@@ -125,6 +125,9 @@ pub trait MCDatabase: std::marker::Send + std::marker::Sync + CloneSPDatabase {
 
     /// update user's password
     async fn update_password(&self, p: &NameHash) -> DBResult<()>;
+
+    /// update username
+    async fn update_username(&self, current: &str, new: &str) -> DBResult<()>;
 }
 
 /// Trait to clone MCDatabase
diff --git a/db/db-core/src/tests.rs b/db/db-core/src/tests.rs
index e2ef2098..5323c298 100644
--- a/db/db-core/src/tests.rs
+++ b/db/db-core/src/tests.rs
@@ -66,10 +66,23 @@ pub async fn database_works<'a, T: MCDatabase>(db: &T, p: &Register<'a>) {
     );
     assert_eq!(name_hash.username, p.username, "username matches");
 
-    // deleting user for re-registration with email = None
-    db.delete_user(p.username).await.unwrap();
+    // update username to p.email
     assert!(
-        !db.username_exists(p.username).await.unwrap(),
+        !db.username_exists(p.email.as_ref().unwrap()).await.unwrap(),
+        "user with p.email doesn't exist. pre-check to update username to p.email"
+    );
+    db.update_username(p.username, p.email.as_ref().unwrap())
+        .await
+        .unwrap();
+    assert!(
+        db.username_exists(p.email.as_ref().unwrap()).await.unwrap(),
+        "user with p.email exist post-update"
+    );
+
+    // deleting user for re-registration with email = None
+    db.delete_user(p.email.as_ref().unwrap()).await.unwrap();
+    assert!(
+        !db.username_exists(p.email.as_ref().unwrap()).await.unwrap(),
         "user is deleted so username shouldn't exsit"
     );