diff --git a/.github/workflows/build-cysignals.yml b/.github/workflows/build-cysignals.yml
index b4277d9aede..6aed99a33be 100644
--- a/.github/workflows/build-cysignals.yml
+++ b/.github/workflows/build-cysignals.yml
@@ -77,7 +77,11 @@ jobs:
           path: python-wheels
           persist-credentials: false
 
+      # 1.13.0 needs its pyproject.toml's cpython-freethreading enable group
+      # dropped (cibuildwheel 3.0+ rejects it); upstream removed it in 1.13.1,
+      # so later versions may have no patches/ directory at all.
       - name: Patch cysignals source
+        if: hashFiles(format('python-wheels/patches/cysignals/{0}/*.patch', env.CYSIGNALS_VERSION)) != ''
         run: git apply python-wheels/patches/cysignals/${{ env.CYSIGNALS_VERSION }}/00*.patch
 
       - name: Build wheels
diff --git a/docs/packages/cysignals.yaml b/docs/packages/cysignals.yaml
index 7b68808fabb..652e1b5efe1 100644
--- a/docs/packages/cysignals.yaml
+++ b/docs/packages/cysignals.yaml
@@ -52,3 +52,4 @@ versions:
   - filename: cysignals-1.13.0-cp314-cp314t-musllinux_1_2_riscv64.whl
     sha256: df3ca8fcebce8b05b59a61d65fdcaf5fe3afcdb6967f672aab586ca80aee62c2
     requires-python: '>=3.13'
+- version: 1.13.1