diff --git a/.github/workflows/client_js.yml b/.github/workflows/client_js.yml
index 77a6b6c..4dc26e5 100644
--- a/.github/workflows/client_js.yml
+++ b/.github/workflows/client_js.yml
@@ -61,6 +61,15 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Verify tag is on main branch
+        run: |
+          if ! git merge-base --is-ancestor ${{ github.sha }} origin/main; then
+            echo "::error::Tag must be on the main branch"
+            exit 1
+          fi
 
       - name: Set up Node.js
         uses: actions/setup-node@v4
diff --git a/.github/workflows/client_react.yml b/.github/workflows/client_react.yml
index 4e307bd..a8cdf0e 100644
--- a/.github/workflows/client_react.yml
+++ b/.github/workflows/client_react.yml
@@ -61,6 +61,15 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Verify tag is on main branch
+        run: |
+          if ! git merge-base --is-ancestor ${{ github.sha }} origin/main; then
+            echo "::error::Tag must be on the main branch"
+            exit 1
+          fi
 
       - name: Set up Node.js
         uses: actions/setup-node@v4
diff --git a/.github/workflows/server_ex.yml b/.github/workflows/server_ex.yml
index 458a915..babb944 100644
--- a/.github/workflows/server_ex.yml
+++ b/.github/workflows/server_ex.yml
@@ -67,6 +67,15 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Verify tag is on main branch
+        run: |
+          if ! git merge-base --is-ancestor ${{ github.sha }} origin/main; then
+            echo "::error::Tag must be on the main branch"
+            exit 1
+          fi
 
       - name: Set up Elixir
         uses: erlef/setup-beam@v1
diff --git a/client_react/CHANGELOG.md b/client_react/CHANGELOG.md
index a8626ad..7a9d2e1 100644
--- a/client_react/CHANGELOG.md
+++ b/client_react/CHANGELOG.md
@@ -1,5 +1,11 @@
 # CHANGELOG
 
+## 0.3.6
+
+### Fixes
+
+- Update core dependency to fix merging into undefined existing value.
+
 ## 0.3.5
 
 ### Features
diff --git a/client_react/package-lock.json b/client_react/package-lock.json
index 9a2f12f..4ecc846 100644
--- a/client_react/package-lock.json
+++ b/client_react/package-lock.json
@@ -1,15 +1,15 @@
 {
   "name": "@topical/react",
-  "version": "0.3.4",
+  "version": "0.3.5",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
       "name": "@topical/react",
-      "version": "0.3.4",
+      "version": "0.3.5",
       "license": "Apache-2.0",
       "dependencies": {
-        "@topical/core": "^0.3.1"
+        "@topical/core": "^0.3.2"
       },
       "devDependencies": {
         "@biomejs/biome": "^2.3.11",
@@ -184,9 +184,9 @@
       }
     },
     "node_modules/@topical/core": {
-      "version": "0.3.1",
-      "resolved": "https://registry.npmjs.org/@topical/core/-/core-0.3.1.tgz",
-      "integrity": "sha512-T4ovU46XBf/iAah6XXdWo8VFkWVHQNTHHPIPlrWHa9rmXR59nw6VdkxmeBhcwlBLsJ/6OFqDFkVb5DhoXskADQ==",
+      "version": "0.3.2",
+      "resolved": "https://registry.npmjs.org/@topical/core/-/core-0.3.2.tgz",
+      "integrity": "sha512-NY7a/9Hdc48QuNG7UNdrhvPVSEkuvc78vo47LBWOEUoN7kGh6nU/mgiz+VU9LTqYvQ/dDfDT7iUogi8jkHOdeg==",
       "license": "Apache-2.0"
     },
     "node_modules/@types/prop-types": {
@@ -337,9 +337,9 @@
       "optional": true
     },
     "@topical/core": {
-      "version": "0.3.1",
-      "resolved": "https://registry.npmjs.org/@topical/core/-/core-0.3.1.tgz",
-      "integrity": "sha512-T4ovU46XBf/iAah6XXdWo8VFkWVHQNTHHPIPlrWHa9rmXR59nw6VdkxmeBhcwlBLsJ/6OFqDFkVb5DhoXskADQ=="
+      "version": "0.3.2",
+      "resolved": "https://registry.npmjs.org/@topical/core/-/core-0.3.2.tgz",
+      "integrity": "sha512-NY7a/9Hdc48QuNG7UNdrhvPVSEkuvc78vo47LBWOEUoN7kGh6nU/mgiz+VU9LTqYvQ/dDfDT7iUogi8jkHOdeg=="
     },
     "@types/prop-types": {
       "version": "15.7.5",
diff --git a/client_react/package.json b/client_react/package.json
index 8b2850a..fa12c04 100644
--- a/client_react/package.json
+++ b/client_react/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@topical/react",
-  "version": "0.3.5",
+  "version": "0.3.6",
   "description": "React Topical client.",
   "main": "dist/index.js",
   "typings": "dist/index.d.ts",
@@ -33,6 +33,6 @@
     "typescript": "^5.9.3"
   },
   "dependencies": {
-    "@topical/core": "^0.3.1"
+    "@topical/core": "^0.3.2"
   }
 }