diff --git a/zerver/lib/dev_ldap_directory.py b/zerver/lib/dev_ldap_directory.py
index 9333ae089a..a6dac58c19 100644
--- a/zerver/lib/dev_ldap_directory.py
+++ b/zerver/lib/dev_ldap_directory.py
@@ -25,7 +25,7 @@ def generate_dev_ldap_dir(mode: str, num_users: int=8) -> Dict[str, Dict[str, An
             email_username = email.split('@')[0]
             ldap_dir['uid=' + email + ',ou=users,dc=zulip,dc=com'] = {
                 'cn': [name[0], ],
-                'userPassword':  email_username,
+                'userPassword':  [email_username, ],
                 'thumbnailPhoto': [profile_images[i % len(profile_images)], ],
                 'userAccountControl': [LDAP_USER_ACCOUNT_CONTROL_NORMAL, ],
             }
@@ -34,7 +34,7 @@ def generate_dev_ldap_dir(mode: str, num_users: int=8) -> Dict[str, Dict[str, An
             email_username = email.split('@')[0]
             ldap_dir['uid=' + email_username + ',ou=users,dc=zulip,dc=com'] = {
                 'cn': [name[0], ],
-                'userPassword': email_username,
+                'userPassword': [email_username, ],
                 'jpegPhoto': [profile_images[i % len(profile_images)], ],
             }
         elif mode == 'c':
@@ -42,7 +42,7 @@ def generate_dev_ldap_dir(mode: str, num_users: int=8) -> Dict[str, Dict[str, An
             email_username = email.split('@')[0]
             ldap_dir['uid=' + email_username + ',ou=users,dc=zulip,dc=com'] = {
                 'cn': [name[0], ],
-                'userPassword': email_username + '_test',
+                'userPassword': [email_username + '_test', ],
                 'email': email,
             }
 
diff --git a/zerver/tests/test_auth_backends.py b/zerver/tests/test_auth_backends.py
index e83edf3385..c978f0b8d0 100644
--- a/zerver/tests/test_auth_backends.py
+++ b/zerver/tests/test_auth_backends.py
@@ -1428,7 +1428,7 @@ class FetchAPIKeyTest(ZulipTestCase):
 
         self.mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing'
+                'userPassword': ['testing', ]
             }
         }
         with self.settings(
@@ -1681,7 +1681,7 @@ class TestTwoFactor(ZulipTestCase):
         full_name = 'New LDAP fullname'
         mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': [full_name],
                 'sn': ['shortname'],
             }
@@ -2162,11 +2162,25 @@ class TestLDAP(ZulipLDAPTestCase):
             self.assertTrue(regex.match(key))
             self.assertCountEqual(list(value.keys()), ['cn', 'userPassword', 'email'])
 
+    @override_settings(AUTHENTICATION_BACKENDS=('zproject.backends.ZulipLDAPAuthBackend',))
+    def test_dev_ldap_fail_login(self) -> None:
+        # Tests that login with a substring of password fails. We had a bug in
+        # dev LDAP environment that allowed login via password substrings.
+        self.mock_ldap.directory = generate_dev_ldap_dir('B', 8)
+        with self.settings(
+                LDAP_APPEND_DOMAIN='zulip.com',
+                AUTH_LDAP_BIND_PASSWORD='',
+                AUTH_LDAP_USER_DN_TEMPLATE='uid=%(user)s,ou=users,dc=zulip,dc=com'):
+            user_profile = self.backend.authenticate('ldapuser1', 'dapu',
+                                                     realm=get_realm('zulip'))
+
+            assert(user_profile is None)
+
     @override_settings(AUTHENTICATION_BACKENDS=('zproject.backends.ZulipLDAPAuthBackend',))
     def test_login_success(self) -> None:
         self.mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing'
+                'userPassword': ['testing', ]
             }
         }
         with self.settings(
@@ -2183,7 +2197,7 @@ class TestLDAP(ZulipLDAPTestCase):
     def test_login_success_with_username(self) -> None:
         self.mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing'
+                'userPassword': ['testing', ]
             }
         }
         with self.settings(
@@ -2200,7 +2214,7 @@ class TestLDAP(ZulipLDAPTestCase):
     def test_login_success_with_email_attr(self) -> None:
         self.mock_ldap.directory = {
             'uid=letham,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'email': ['hamlet@zulip.com'],
             }
         }
@@ -2217,7 +2231,7 @@ class TestLDAP(ZulipLDAPTestCase):
     def test_login_failure_due_to_wrong_password(self) -> None:
         self.mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing'
+                'userPassword': ['testing', ]
             }
         }
         with self.settings(
@@ -2231,7 +2245,7 @@ class TestLDAP(ZulipLDAPTestCase):
     def test_login_failure_due_to_nonexistent_user(self) -> None:
         self.mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing'
+                'userPassword': ['testing', ]
             }
         }
         with self.settings(
@@ -2373,7 +2387,7 @@ class TestLDAP(ZulipLDAPTestCase):
     def test_login_failure_due_to_wrong_subdomain(self) -> None:
         self.mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing'
+                'userPassword': ['testing', ]
             }
         }
         with self.settings(
@@ -2388,7 +2402,7 @@ class TestLDAP(ZulipLDAPTestCase):
     def test_login_failure_due_to_invalid_subdomain(self) -> None:
         self.mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing'
+                'userPassword': ['testing', ]
             }
         }
         with self.settings(
@@ -2403,7 +2417,7 @@ class TestLDAP(ZulipLDAPTestCase):
     def test_login_success_with_valid_subdomain(self) -> None:
         self.mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing'
+                'userPassword': ['testing', ]
             }
         }
         with self.settings(
@@ -2419,7 +2433,7 @@ class TestLDAP(ZulipLDAPTestCase):
     def test_login_failure_due_to_deactivated_user(self) -> None:
         self.mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing'
+                'userPassword': ['testing', ]
             }
         }
         user_profile = self.example_user("hamlet")
@@ -2442,7 +2456,7 @@ class TestLDAP(ZulipLDAPTestCase):
         self.mock_ldap.directory = {
             'uid=nonexisting,ou=users,dc=acme,dc=com': {
                 'cn': ['NonExisting', ],
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'thumbnailPhoto': [open(os.path.join(settings.STATIC_ROOT, "images/team/tim.png"), "rb").read()],
             }
         }
@@ -2468,7 +2482,7 @@ class TestLDAP(ZulipLDAPTestCase):
             'uid=nonexisting,ou=users,dc=acme,dc=com': {
                 'fn': ['Non', ],
                 'ln': ['Existing', ],
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
             }
         }
         with self.settings(
diff --git a/zerver/tests/test_notifications.py b/zerver/tests/test_notifications.py
index 6c92d3ef87..f781ab5f2b 100644
--- a/zerver/tests/test_notifications.py
+++ b/zerver/tests/test_notifications.py
@@ -68,7 +68,7 @@ class TestFollowupEmails(ZulipTestCase):
 
         mock_ldap.directory = {
             "uid=newuser@zulip.com,ou=users,dc=zulip,dc=com": {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': ['full_name'],
                 'sn': ['shortname'],
             }
@@ -100,7 +100,7 @@ class TestFollowupEmails(ZulipTestCase):
 
         mock_ldap.directory = {
             'uid=newuser,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': ['full_name'],
                 'sn': ['shortname'],
             }
@@ -133,7 +133,7 @@ class TestFollowupEmails(ZulipTestCase):
 
         mock_ldap.directory = {
             'uid=newuser,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': ['full_name'],
                 'sn': ['shortname'],
                 'email': ['newuser_email@zulip.com'],
diff --git a/zerver/tests/test_settings.py b/zerver/tests/test_settings.py
index a0799f4e75..2b6b1514c4 100644
--- a/zerver/tests/test_settings.py
+++ b/zerver/tests/test_settings.py
@@ -199,7 +199,7 @@ class ChangeSettingsTest(ZulipTestCase):
 
         mock_ldap.directory = {
             'uid=hamlet,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'ldappassword',
+                'userPassword': ['ldappassword', ],
                 'fn': ['New LDAP fullname']
             }
         }
diff --git a/zerver/tests/test_signup.py b/zerver/tests/test_signup.py
index 7c771aa946..1a7e5a1251 100644
--- a/zerver/tests/test_signup.py
+++ b/zerver/tests/test_signup.py
@@ -2409,7 +2409,7 @@ class UserSignUpTest(ZulipTestCase):
 
         mock_ldap.directory = {
             'uid=newuser,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': ['New LDAP fullname']
             }
         }
@@ -2464,7 +2464,7 @@ class UserSignUpTest(ZulipTestCase):
             # Test the TypeError exception handler
             mock_ldap.directory = {
                 'uid=newuser,ou=users,dc=zulip,dc=com': {
-                    'userPassword': 'testing',
+                    'userPassword': ['testing', ],
                     'fn': None  # This will raise TypeError
                 }
             }
@@ -2494,7 +2494,7 @@ class UserSignUpTest(ZulipTestCase):
         full_name = 'New LDAP fullname'
         mock_ldap.directory = {
             'uid=newuser,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': [full_name],
                 'sn': ['shortname'],
             }
@@ -2566,7 +2566,7 @@ class UserSignUpTest(ZulipTestCase):
 
         mock_ldap.directory = {
             'uid=newuser,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': ['First'],
                 'ln': ['Last'],
             }
@@ -2636,7 +2636,7 @@ class UserSignUpTest(ZulipTestCase):
         full_name = 'New LDAP fullname'
         mock_ldap.directory = {
             'uid=newuser,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': [full_name],
                 'sn': ['shortname'],
             }
@@ -2672,7 +2672,7 @@ class UserSignUpTest(ZulipTestCase):
 
         mock_ldap.directory = {
             'uid=newuser,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': ['New LDAP fullname'],
                 'sn': ['New LDAP shortname'],
             }
@@ -2730,7 +2730,7 @@ class UserSignUpTest(ZulipTestCase):
 
         mock_ldap.directory = {
             'uid=newuser,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': ['New LDAP fullname'],
                 'sn': ['New LDAP shortname'],
             }
@@ -2845,7 +2845,7 @@ class UserSignUpTest(ZulipTestCase):
 
         mock_ldap.directory = {
             'uid=newuser,ou=users,dc=zulip,dc=com': {
-                'userPassword': 'testing',
+                'userPassword': ['testing', ],
                 'fn': ['New User Name']
             }
         }