diff --git a/awx/api/serializers.py b/awx/api/serializers.py
index a5d6f9a4e1..38ca992021 100644
--- a/awx/api/serializers.py
+++ b/awx/api/serializers.py
@@ -2036,6 +2036,7 @@ class CredentialSerializer(BaseSerializer):
         return ret
 
     def to_internal_value(self, data):
+        # TODO: remove when API v1 is removed
         if 'credential_type' not in data:
             # If `credential_type` is not provided, assume the payload is a
             # v1 credential payload that specifies a `kind` and a flat list
@@ -2050,6 +2051,21 @@ class CredentialSerializer(BaseSerializer):
                 {'credential_type': credential_type}.items() +
                 super(CredentialSerializer, self).to_internal_value(data).items()
             )
+
+            # Make a set of the keys in the POST/PUT payload
+            # - Subtract real fields (name, organization, inputs)
+            # - Subtract virtual v1 fields defined on the determined credential
+            #   type (username, password, etc...)
+            # - Any leftovers are invalid for the determined credential type
+            valid_fields = set(super(CredentialSerializer, self).get_fields().keys())
+            valid_fields.update(V2CredentialFields().get_fields().keys())
+            valid_fields.update(['kind', 'cloud'])
+
+            for field in set(data.keys()) - valid_fields - set(credential_type.defined_fields):
+                if data.get(field):
+                    raise serializers.ValidationError(
+                        {"detail": _("'%s' is not a valid field for %s") % (field, credential_type.name)}
+                    )
             value.pop('kind', None)
             return value
         return super(CredentialSerializer, self).to_internal_value(data)
diff --git a/awx/main/models/credential.py b/awx/main/models/credential.py
index ccded60c38..806c681cff 100644
--- a/awx/main/models/credential.py
+++ b/awx/main/models/credential.py
@@ -473,7 +473,7 @@ class CredentialType(CommonModelNameNotUnique):
         kind_choices = dict(V1Credential.KIND_CHOICES)
         requirements = {}
         if kind == 'ssh':
-            if 'vault_password' in data:
+            if data.get('vault_password'):
                 requirements['kind'] = 'vault'
             else:
                 requirements['kind'] = 'ssh'
diff --git a/awx/main/tests/functional/api/test_credential.py b/awx/main/tests/functional/api/test_credential.py
index 45096c2433..e837594866 100644
--- a/awx/main/tests/functional/api/test_credential.py
+++ b/awx/main/tests/functional/api/test_credential.py
@@ -681,6 +681,61 @@ def test_scm_create_ok(post, organization, admin, version, params):
     assert decrypt_field(cred, 'ssh_key_unlock') == 'some_key_unlock'
 
 
+@pytest.mark.django_db
+@pytest.mark.parametrize('version, params', [
+    ['v1', {
+        'kind': 'ssh',
+        'name': 'Best credential ever',
+        'password': 'secret',
+        'vault_password': '',
+    }],
+    ['v2', {
+        'credential_type': 1,
+        'name': 'Best credential ever',
+        'inputs': {
+            'password': 'secret',
+        }
+    }]
+])
+def test_ssh_create_ok(post, organization, admin, version, params):
+    ssh = CredentialType.defaults['ssh']()
+    ssh.save()
+    params['organization'] = organization.id
+    response = post(
+        reverse('api:credential_list', kwargs={'version': version}),
+        params,
+        admin
+    )
+    assert response.status_code == 201
+
+    assert Credential.objects.count() == 1
+    cred = Credential.objects.all()[:1].get()
+    assert cred.credential_type == ssh
+    assert decrypt_field(cred, 'password') == 'secret'
+
+
+@pytest.mark.django_db
+def test_v1_ssh_vault_ambiguity(post, organization, admin):
+    vault = CredentialType.defaults['vault']()
+    vault.save()
+    params = {
+        'organization': organization.id,
+        'kind': 'ssh',
+        'name': 'Best credential ever',
+        'username': 'joe',
+        'password': 'secret',
+        'ssh_key_data': 'some_key_data',
+        'ssh_key_unlock': 'some_key_unlock',
+        'vault_password': 'vault_password',
+    }
+    response = post(
+        reverse('api:credential_list', kwargs={'version': 'v1'}),
+        params,
+        admin
+    )
+    assert response.status_code == 400
+
+
 #
 # Vault Credentials
 #