diff --git a/.github/workflows/release-artifacts.yml b/.github/workflows/release-artifacts.yml
index 3773b97c7..5d4a4fe1d 100644
--- a/.github/workflows/release-artifacts.yml
+++ b/.github/workflows/release-artifacts.yml
@@ -92,7 +92,7 @@ jobs:
           mv /tmp/.buildx-cache-new /tmp/.buildx-cache
 
       - name: Upload debs as artifacts
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3 # Don't upgrade to v4; broken: https://github.com/actions/upload-artifact#breaking-changes
         with:
           name: debs
           path: debs/*
@@ -156,7 +156,7 @@ jobs:
           CARGO_NET_GIT_FETCH_WITH_CLI: true
           CIBW_ENVIRONMENT_PASS_LINUX: CARGO_NET_GIT_FETCH_WITH_CLI
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v3 # Don't upgrade to v4; broken: https://github.com/actions/upload-artifact#breaking-changes
         with:
           name: Wheel
           path: ./wheelhouse/*.whl
@@ -177,7 +177,7 @@ jobs:
       - name: Build sdist
         run: python -m build --sdist
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v3 # Don't upgrade to v4; broken: https://github.com/actions/upload-artifact#breaking-changes
         with:
           name: Sdist
           path: dist/*.tar.gz
@@ -194,7 +194,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Download all workflow run artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v3 # Don't upgrade to v4, it should match upload-artifact
       - name: Build a tarball for the debs
         run: tar -cvJf debs.tar.xz debs
       - name: Attach to release
diff --git a/CHANGES.md b/CHANGES.md
index 4bef78409..e9478ea1a 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,16 @@
+# Synapse 1.100.0rc2 (2024-01-24)
+
+This version is the same as 1.100.0rc1 but with fixes to the release process.
+
+### Internal Changes
+
+- Downgrade the `download-artifact` and `upload-artifact` actions to v3 due to breaking changes. ([\#16847](https://github.com/element-hq/synapse/issues/16847))
+
+
 # Synapse 1.100.0rc1 (2024-01-23)
 
+*This version was never released to PyPI or the Debian repository due to failures in the automatic part of the release process.*
+
 ### Features
 
 - Advertise experimental support for [MSC4028](https://github.com/matrix-org/matrix-spec-proposals/pull/4028) through `/_matrix/clients/versions` if enabled. Contributed by @hanadi92. ([\#16787](https://github.com/element-hq/synapse/issues/16787))
diff --git a/debian/changelog b/debian/changelog
index ca0e2aec4..5a86b6302 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+matrix-synapse-py3 (1.100.0~rc2) stable; urgency=medium
+
+  * New Synapse release 1.100.0rc2.
+
+ -- Synapse Packaging team <packages@matrix.org>  Wed, 24 Jan 2024 11:59:51 +0000
+
 matrix-synapse-py3 (1.100.0~rc1) stable; urgency=medium
 
   * New Synapse release 1.100.0rc1.
diff --git a/pyproject.toml b/pyproject.toml
index 3bfbb1cc4..d4cb01f7c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -96,7 +96,7 @@ module-name = "synapse.synapse_rust"
 
 [tool.poetry]
 name = "matrix-synapse"
-version = "1.100.0rc1"
+version = "1.100.0rc2"
 description = "Homeserver for the Matrix decentralised comms protocol"
 authors = ["Matrix.org Team and Contributors <packages@matrix.org>"]
 license = "AGPL-3.0-or-later"