diff --git a/.semaphore/semaphore.yml b/.semaphore/semaphore.yml
index 3c6e4e4..c784416 100644
--- a/.semaphore/semaphore.yml
+++ b/.semaphore/semaphore.yml
@@ -3,7 +3,7 @@ name: Mast docker build
 agent:
   machine:
     type: e1-standard-4
-    os_image: ubuntu1804
+    os_image: ubuntu2004
 blocks:
   - name: build
     task:
@@ -17,7 +17,7 @@ blocks:
         - name: build
           commands:
             - checkout
-            - sem-version python 3.6
+            - sem-version python 3.9
             - cache restore ${SEMAPHORE_GIT_BRANCH}-pip
             - pip install --quiet --no-color .[ci]
             - cache delete ${SEMAPHORE_GIT_BRANCH}-pip
@@ -43,7 +43,7 @@ blocks:
         - name: deploy
           commands:
             - checkout
-            - sem-version python 3.6
+            - sem-version python 3.9
             - git config --global user.email "semaphore@example.org"
             - git config --global user.name "Semaphore CI"
             - cache restore ${SEMAPHORE_GIT_BRANCH}-${SEMAPHORE_WORKFLOW_ID}-build
diff --git a/Dockerfile b/Dockerfile
index 4b82977..c1853f6 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -13,10 +13,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM python:3.6-alpine3.7 as common
+FROM python:3.9-alpine3.19 as common
 LABEL maintainer="fiaas <fiaas@googlegroups.com>"
 
-RUN apk --no-cache add --update ca-certificates tini=0.16.1-r0 yaml && \
+RUN apk --no-cache add --update ca-certificates tini=0.19.0-r2 yaml && \
     mkdir -p /opt/fiaas-mast && \
     adduser -u 10001 -D -h /opt/fiaas-mast fiaas-mast
 
diff --git a/README.md b/README.md
index b129c82..03e44a2 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@ Kubernetes cluster.
 Development
 -----------
 
-The Development target is Python 3.6.
+The Development target is Python 3.9.
 
 Install dependencies using `pip`:
 
diff --git a/fiaas_mast/fiaas.py b/fiaas_mast/fiaas.py
index 6a37de2..25d907d 100644
--- a/fiaas_mast/fiaas.py
+++ b/fiaas_mast/fiaas.py
@@ -17,7 +17,6 @@
 
 from __future__ import absolute_import
 
-import six
 from k8s.base import Model
 from k8s.fields import Field, RequiredField, ListField
 from k8s.models.common import ObjectMeta
@@ -34,8 +33,8 @@ class AdditionalLabelsOrAnnotations(Model):
 
 
 class FiaasApplicationSpec(Model):
-    application = RequiredField(six.text_type)
-    image = RequiredField(six.text_type)
+    application = RequiredField(str)
+    image = RequiredField(str)
     config = RequiredField(dict)
     additional_labels = Field(AdditionalLabelsOrAnnotations)
     additional_annotations = Field(AdditionalLabelsOrAnnotations)
@@ -47,8 +46,8 @@ class Meta:
         watch_list_url = "/apis/fiaas.schibsted.io/v1/watch/applications"
 
     # Workaround for https://github.com/kubernetes/kubernetes/issues/44182
-    apiVersion = Field(six.text_type, "fiaas.schibsted.io/v1")
-    kind = Field(six.text_type, "Application")
+    apiVersion = Field(str, "fiaas.schibsted.io/v1")
+    kind = Field(str, "Application")
 
     metadata = Field(ObjectMeta)
     spec = Field(FiaasApplicationSpec)
@@ -60,12 +59,12 @@ class Meta:
         url_template = "/apis/fiaas.schibsted.io/v1/namespaces/{namespace}/statuses/{name}"
 
     # Workaround for https://github.com/kubernetes/kubernetes/issues/44182
-    apiVersion = Field(six.text_type, "fiaas.schibsted.io/v1")
-    kind = Field(six.text_type, "Status")
+    apiVersion = Field(str, "fiaas.schibsted.io/v1")
+    kind = Field(str, "Status")
 
     metadata = Field(ObjectMeta)
-    result = Field(six.text_type)
-    logs = ListField(six.text_type)
+    result = Field(str)
+    logs = ListField(str)
 
 
 class FiaasApplicationStatus(Model):
@@ -73,9 +72,9 @@ class Meta:
         url_template = "/apis/fiaas.schibsted.io/v1/namespaces/{namespace}/application-statuses/{name}"
 
     # Workaround for https://github.com/kubernetes/kubernetes/issues/44182
-    apiVersion = Field(six.text_type, "fiaas.schibsted.io/v1")
-    kind = Field(six.text_type, "ApplicationStatus")
+    apiVersion = Field(str, "fiaas.schibsted.io/v1")
+    kind = Field(str, "ApplicationStatus")
 
     metadata = Field(ObjectMeta)
-    result = Field(six.text_type)
-    logs = ListField(six.text_type)
+    result = Field(str)
+    logs = ListField(str)
diff --git a/setup.py b/setup.py
index cdb5a2d..d3a88dc 100644
--- a/setup.py
+++ b/setup.py
@@ -39,11 +39,15 @@ def version():
     "Flask==1.1.1",
     "flask-talisman==0.7.0",
     "flask-bootstrap==3.3.7.1",
+    "itsdangerous==2.0.1", # pinned for Flask 1.x
+    "jinja2==3.0.3", # pinned for flask 1.x
+    "markupsafe==2.0.1", # pinned for flask 1.x
+    "werkzeug==2.0.3", # pinned for flask 1.x
     "pyyaml>=5.4",
-    "requests==2.22.0",
-    "six==1.12.0",
+    "requests==2.31.0",
+    "urllib3==1.26.17",
     "ipaddress==1.0.22",
-    "k8s==0.21.0",
+    "k8s==0.24.2",
     "prometheus_client == 0.7.1",
 ]
 
@@ -52,12 +56,10 @@ def version():
 ]
 
 CI_REQ = [
-    "tox==3.13.2",
-    "tox-travis==0.12",
+    "tox==3.28.0",
 ]
 
 TEST_REQ = [
-    'mock==3.0.5',
     'pytest-sugar==0.9.2',
     'pytest==3.10.1',
     "pytest-cov==2.7.1",
diff --git a/tests/test_common.py b/tests/test_common.py
index 175f875..5a04f0e 100644
--- a/tests/test_common.py
+++ b/tests/test_common.py
@@ -17,7 +17,7 @@
 
 import pytest
 from k8s.client import NotFound
-from mock import patch
+from unittest.mock import patch
 
 from fiaas_mast.common import check_models, PlatformError
 from fiaas_mast.fiaas import FiaasApplication, FiaasApplicationSpec
diff --git a/tests/test_deployer.py b/tests/test_deployer.py
index 93f6dc2..ef811cc 100644
--- a/tests/test_deployer.py
+++ b/tests/test_deployer.py
@@ -16,7 +16,7 @@
 import pytest
 import yaml
 from k8s.models.common import ObjectMeta
-from mock import MagicMock, patch
+from unittest.mock import MagicMock, patch
 
 from fiaas_mast.deployer import generate_random_uuid_string, Deployer
 from fiaas_mast.fiaas import FiaasApplicationSpec, FiaasApplication
diff --git a/tests/test_generator.py b/tests/test_generator.py
index b1974da..a2b2869 100644
--- a/tests/test_generator.py
+++ b/tests/test_generator.py
@@ -13,9 +13,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import mock
+from unittest import mock
 import pytest
-from mock import MagicMock
+from unittest.mock import MagicMock
 
 from fiaas_mast.application_generator import ApplicationGenerator
 from fiaas_mast.common import generate_random_uuid_string
diff --git a/tests/test_status.py b/tests/test_status.py
index 8abf20a..a66468b 100644
--- a/tests/test_status.py
+++ b/tests/test_status.py
@@ -16,7 +16,7 @@
 # limitations under the License.
 
 
-import mock
+from unittest import mock
 import os.path
 import pytest
 import yaml
diff --git a/tests/test_web.py b/tests/test_web.py
index 9eb442a..01f1030 100644
--- a/tests/test_web.py
+++ b/tests/test_web.py
@@ -16,7 +16,7 @@
 from json import loads, dumps
 from urllib.parse import urlparse
 
-import mock
+from unittest import mock
 import pytest
 
 from fiaas_mast.app import create_app
diff --git a/tox.ini b/tox.ini
index 27fbc76..82e24b0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 
 [tox]
-envlist = py36
+envlist = py39
 skip_missing_interpreters=True
 
 [testenv]