diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 820c17b..51dfc57 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: "Build library source and wheel artifacts"
-        uses: ansys/actions/build-library@v9
+        uses: ansys/actions/build-library@v10
         with:
           library-name: ${{ env.PACKAGE_NAME }}
 
@@ -47,7 +47,7 @@ jobs:
     if: github.event_name == 'push' && contains(github.ref, 'refs/tags')
     steps:
       - name: "Release to the public PyPI repository"
-        uses: ansys/actions/release-pypi-public@v9
+        uses: ansys/actions/release-pypi-public@v10
         with:
           library-name:  ${{ env.PACKAGE_NAME }}
           twine-username: "__token__"
diff --git a/src/ansys/api/acp/VERSION b/src/ansys/api/acp/VERSION
index 0d91a54..9e11b32 100644
--- a/src/ansys/api/acp/VERSION
+++ b/src/ansys/api/acp/VERSION
@@ -1 +1 @@
-0.3.0
+0.3.1
diff --git a/src/ansys/api/acp/v0/stackup.proto b/src/ansys/api/acp/v0/stackup.proto
index e9c9e17..cded299 100644
--- a/src/ansys/api/acp/v0/stackup.proto
+++ b/src/ansys/api/acp/v0/stackup.proto
@@ -53,8 +53,8 @@ message Properties {
     base.ResourcePath cut_off_material = 11;
 
     // read only properties
-    double thickness = 12;
-    double area_weight = 13;
+    optional double thickness = 12;
+    optional double area_weight = 13;
 }
 
 message ObjectInfo {