diff --git a/.github/workflows/build-pydantic-monty-client.yml b/.github/workflows/build-pydantic-monty-client.yml
index 169a0afa7dcc..18ba71d0a7dd 100644
--- a/.github/workflows/build-pydantic-monty-client.yml
+++ b/.github/workflows/build-pydantic-monty-client.yml
@@ -58,11 +58,26 @@ jobs:
       MONTY_VERSION: ${{ matrix.version }}
 
     steps:
+      # Upstream tags older releases `vX.Y.Z` and newer ones plain `X.Y.Z`; use whichever exists.
+      - name: Resolve upstream tag
+        id: tag
+        run: |
+          for ref in "v$VERSION" "$VERSION"; do
+            if git ls-remote --exit-code --tags https://github.com/pydantic/monty "refs/tags/$ref" >/dev/null; then
+              echo "ref=$ref" >> "$GITHUB_OUTPUT"
+              exit 0
+            fi
+          done
+          echo "no tag for $VERSION in pydantic/monty" >&2
+          exit 1
+        env:
+          VERSION: ${{ env.MONTY_VERSION }}
+
       - name: Checkout monty ${{ env.MONTY_VERSION }}
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
         with:
           repository: pydantic/monty
-          ref: v${{ env.MONTY_VERSION }}
+          ref: ${{ steps.tag.outputs.ref }}
           persist-credentials: false
 
       # `crates/monty-python`'s pyproject.toml has no `license-files`, so
diff --git a/docs/packages/pydantic-monty-client.yaml b/docs/packages/pydantic-monty-client.yaml
index e124f0795afa..d5c4c5508818 100644
--- a/docs/packages/pydantic-monty-client.yaml
+++ b/docs/packages/pydantic-monty-client.yaml
@@ -107,3 +107,4 @@ versions:
   - filename: pydantic_monty_client-1.3.0-cp314-cp314t-manylinux_2_39_riscv64.whl
     sha256: 64c8f8cc65f1ae72fa52e3681e8b39040bf0881bd3958868d4cb53746ce4f570
     requires-python: '>=3.10'
+- version: 1.4.0