diff --git a/moto/cognitoidp/models.py b/moto/cognitoidp/models.py
index fb77e66881ef..15aa01455bf6 100644
--- a/moto/cognitoidp/models.py
+++ b/moto/cognitoidp/models.py
@@ -1525,7 +1525,7 @@ def initiate_auth(self, client_id, auth_flow, auth_parameters):
                 "ChallengeParameters": {
                     "SALT": uuid.uuid4().hex,
                     "SRP_B": uuid.uuid4().hex,
-                    "USERNAME": user.id,
+                    "USERNAME": user.username,
                     "USER_ID_FOR_SRP": user.id,
                     "SECRET_BLOCK": session,
                 },
diff --git a/tests/test_cognitoidp/test_cognitoidp.py b/tests/test_cognitoidp/test_cognitoidp.py
index 1219be4b6c69..671c179bdbca 100644
--- a/tests/test_cognitoidp/test_cognitoidp.py
+++ b/tests/test_cognitoidp/test_cognitoidp.py
@@ -2561,6 +2561,7 @@ def user_authentication_flow(conn):
 
     result["AuthenticationResult"]["IdToken"].should_not.be.none
     result["AuthenticationResult"]["AccessToken"].should_not.be.none
+    result["AuthenticationResult"]["TokenType"].should.equal("Bearer")
 
     # authenticate user once again this time with mfa token
     result = conn.initiate_auth(
@@ -3317,6 +3318,7 @@ def test_initiate_auth_USER_SRP_AUTH():
     )
 
     result["ChallengeName"].should.equal("PASSWORD_VERIFIER")
+    result["ChallengeParameters"]["USERNAME"].should.equal(username)
 
 
 @mock_cognitoidp
@@ -3385,6 +3387,7 @@ def test_initiate_auth_USER_PASSWORD_AUTH():
     result["AuthenticationResult"]["AccessToken"].should_not.be.none
     result["AuthenticationResult"]["IdToken"].should_not.be.none
     result["AuthenticationResult"]["RefreshToken"].should_not.be.none
+    result["AuthenticationResult"]["TokenType"].should.equal("Bearer")
 
 
 @mock_cognitoidp