diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6ecb653d15..f0cf2a144a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,27 +6,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.8, 3.7, 3.6, 2.7]
-        plone-version: [5.2, 5.1, 4.3]
-        exclude:
-          - python-version: 3.6
-            plone-version: 4.3
-          - python-version: 3.6
-            plone-version: 5.0
-          - python-version: 3.6
-            plone-version: 5.1
-          - python-version: 3.7
-            plone-version: 4.3
-          - python-version: 3.7
-            plone-version: 5.0
-          - python-version: 3.7
-            plone-version: 5.1
-          - python-version: 3.8
-            plone-version: 4.3
-          - python-version: 3.8
-            plone-version: 5.0
-          - python-version: 3.8
-            plone-version: 5.1
+        python-version: [3.8, 3.7]
+        plone-version: [5.2]
 
     steps:
       # git checkout
@@ -42,7 +23,7 @@ jobs:
       - uses: actions/cache@v1
         with:
           path: ~/.cache/pip
-          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
+          key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}
           restore-keys: |
             ${{ runner.os }}-pip-
 
@@ -64,7 +45,7 @@ jobs:
 
       # build sphinx
       - name: sphinx
-        run: if [ "${{ matrix.plone-version }}" == "5.2" ] && [ ${{ matrix.python-version }} == '3.7' ]; then bin/sphinxbuilder; fi
+        run: if [ "${{ matrix.plone-version }}" == "5.2" ] && [ ${{ matrix.python-version }} == '3.8' ]; then bin/sphinxbuilder; fi
 
       # test
       - name: test
@@ -79,4 +60,53 @@ jobs:
 
       # test sphinx warnings
       - name: sphinx
-        run: if [ "${{ matrix.plone-version }}" == "5.2" ] && [ ${{ matrix.python-version }} == '3.7' ]; then bin/test-no-sphinx-warnings; fi
+        run: if [ "${{ matrix.plone-version }}" == "5.2" ] && [ ${{ matrix.python-version }} == '3.8' ]; then bin/test-no-sphinx-warnings; fi
+
+  build-py2:
+    runs-on: ubuntu-20.04
+    container:
+      image: python:2.7.18-buster
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: [2.7]
+        plone-version: [5.2, 5.1, 4.3]
+
+    steps:
+      # git checkout
+      - uses: actions/checkout@v2
+
+      # python cache
+      - uses: actions/cache@v1
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+
+      # python install
+      - run: pip install virtualenv
+      - run: pip install wheel
+      - name: pip install
+        run: pip install -r requirements.txt
+
+      # buildout
+      - name: buildout
+        run: buildout -t 10 -c plone-${{ matrix.plone-version }}.x.cfg code-analysis:return-status-codes=True
+        env:
+          CI: true
+
+      # code analysis
+      - name: code analysis
+        run: bin/code-analysis
+
+      # test
+      - name: test
+        run: bin/test
+
+      # test no uncommited changes
+      - name: test no uncommited changes
+        run: bin/test-no-uncommitted-doc-changes
+        env:
+          PYTHON_VERSION: ${{ matrix.python-version }}
+          PLONE_VERSION: ${{ matrix.plone-version }}
diff --git a/news/1721.feature b/news/1721.feature
new file mode 100644
index 0000000000..e656fa9b2c
--- /dev/null
+++ b/news/1721.feature
@@ -0,0 +1,2 @@
+New version pins to run tests
+[erral]
diff --git a/plone-4.3.x.cfg b/plone-4.3.x.cfg
index 1278c56a8d..6c5e89d6c5 100644
--- a/plone-4.3.x.cfg
+++ b/plone-4.3.x.cfg
@@ -23,3 +23,9 @@ six = 1.12.0
 
 # latest version compatible with Python 2
 plone.schema = 1.4.0
+
+# latest version compatible with Python 2
+sphinxcontrib-websupport = 1.1.2
+stdlib-list = 0.6.0
+zest.pocompile = 1.6.0
+plone.rest = 3.0.2
diff --git a/plone-5.1.x.cfg b/plone-5.1.x.cfg
index edd3d53367..8854696f9a 100644
--- a/plone-5.1.x.cfg
+++ b/plone-5.1.x.cfg
@@ -15,3 +15,6 @@ pyparsing = 2.4.7
 
 # Required by plone.restapi
 six = 1.12.0
+stdlib-list = 0.6.0
+zest.pocompile= 1.6.0
+plone.rest = 3.0.2
diff --git a/plone-5.2.x.cfg b/plone-5.2.x.cfg
index cbd4374065..00e4cd406f 100644
--- a/plone-5.2.x.cfg
+++ b/plone-5.2.x.cfg
@@ -19,3 +19,4 @@ importlib-metadata = 2.0.0
 
 # latest version compatible with Python 2
 flake8-print = 4.0.1
+zest.pocompile= 1.6.0
diff --git a/src/plone/restapi/tests/test_dxfield_serializer.py b/src/plone/restapi/tests/test_dxfield_serializer.py
index 288992b8fb..0562a25d6e 100644
--- a/src/plone/restapi/tests/test_dxfield_serializer.py
+++ b/src/plone/restapi/tests/test_dxfield_serializer.py
@@ -41,14 +41,20 @@ def setUp(self):
         ]
 
     def serialize(self, fieldname, value):
+        field = None
         for schema in iterSchemata(self.doc1):
             if fieldname in schema:
                 field = schema.get(fieldname)
                 break
-        dm = getMultiAdapter((self.doc1, field), IDataManager)
-        dm.set(value)
-        serializer = getMultiAdapter((field, self.doc1, self.request), IFieldSerializer)
-        return serializer()
+        if field is not None:
+            dm = getMultiAdapter((self.doc1, field), IDataManager)
+            dm.set(value)
+            serializer = getMultiAdapter(
+                (field, self.doc1, self.request), IFieldSerializer
+            )
+            return serializer()
+
+        return None
 
     def test_ascii_field_serialization_returns_unicode(self):
         value = self.serialize("test_ascii_field", "foo")
diff --git a/test-no-uncommitted-doc-changes.in b/test-no-uncommitted-doc-changes.in
index 43e15b81f1..c2ad9929e4 100644
--- a/test-no-uncommitted-doc-changes.in
+++ b/test-no-uncommitted-doc-changes.in
@@ -13,12 +13,12 @@ function red {
     echo "$RED $1 $RESET"
 }
 
-if [ "$PLONE_VERSION" == "5.2" ] && [ "$PYTHON_VERSION" == '3.7' ]; then
-    echo "Running check for undocumented changes for Plone 5.2.x on Python 3.7"
+if [ "$PLONE_VERSION" == "5.2" ] && [ "$PYTHON_VERSION" == '3.8' ]; then
+    echo "Running check for undocumented changes for Plone 5.2.x on Python 3.8"
 else
     # request/response dumps have known differences for Plone 5
     # => skip, we can't have the Plone 5 build fail because of those
-    echo "Skipping checks for undocumented changes for everything except Plone 5.2.x on Python 3.7"
+    echo "Skipping checks for undocumented changes for everything except Plone 5.2.x on Python 3.8"
     exit 0
 fi