diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3a337db9..80360a74 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -33,9 +33,13 @@ jobs:
       matrix:
         rust-version: [stable]
         runs-on: [ubuntu, macos]
+        python-version: ["3.13"]
         include:
           - rust-version: ${{ needs.resolve.outputs.MSRV }}
             runs-on: ubuntu
+          - rust-version: stable
+            runs-on: ubuntu
+            python-version: "3.13t"
           - rust-version: nightly
             runs-on: ubuntu
 
@@ -49,9 +53,9 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: set up python
-        uses: actions/setup-python@v5
+        uses: quansight-labs/setup-python@v5
         with:
-          python-version: "3.13"
+          python-version: ${{ matrix.python-version }}
 
       - uses: dtolnay/rust-toolchain@master
         with:
@@ -78,10 +82,15 @@ jobs:
           token: ${{ secrets.CODECOV_TOKEN }}
 
   test-python:
-    name: test jiter-python
+    name: test jiter-python ${{ matrix.python-version }}
 
     runs-on: ubuntu-latest
 
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.13", "3.13t"]
+
     env:
       RUNS_ON: ubuntu-latest
 
@@ -89,16 +98,16 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: set up python
-        uses: actions/setup-python@v5
+        uses: quansight-labs/setup-python@v5
         with:
-          python-version: "3.13"
+          python-version: ${{ matrix.python-version }}
 
       - uses: dtolnay/rust-toolchain@stable
       - uses: Swatinem/rust-cache@v2
       - uses: taiki-e/install-action@cargo-llvm-cov
 
       - name: Install python dependencies
-        run: make python-install
+        run: pip install -r crates/jiter-python/tests/requirements.txt
 
       - name: Build jiter-python
         run: |
diff --git a/crates/jiter-python/src/lib.rs b/crates/jiter-python/src/lib.rs
index 8488982d..9f080e91 100644
--- a/crates/jiter-python/src/lib.rs
+++ b/crates/jiter-python/src/lib.rs
@@ -58,13 +58,13 @@ mod jiter_python {
     }
 
     #[pyfunction]
-    pub fn cache_clear(py: Python<'_>) {
-        jiter::cache_clear(py);
+    pub fn cache_clear() {
+        jiter::cache_clear();
     }
 
     #[pyfunction]
-    pub fn cache_usage(py: Python<'_>) -> usize {
-        jiter::cache_usage(py)
+    pub fn cache_usage() -> usize {
+        jiter::cache_usage()
     }
 
     #[pymodule_init]
diff --git a/crates/jiter/src/py_string_cache.rs b/crates/jiter/src/py_string_cache.rs
index 874d8811..58728238 100644
--- a/crates/jiter/src/py_string_cache.rs
+++ b/crates/jiter/src/py_string_cache.rs
@@ -1,9 +1,8 @@
-use std::cell::RefCell;
+use std::sync::{Mutex, OnceLock};
 
 use ahash::random_state::RandomState;
 use pyo3::exceptions::{PyTypeError, PyValueError};
 use pyo3::prelude::*;
-use pyo3::sync::{GILOnceCell, GILProtected};
 use pyo3::types::{PyBool, PyString};
 
 #[derive(Debug, Clone, Copy)]
@@ -86,28 +85,34 @@ impl StringMaybeCache for StringNoCache {
     }
 }
 
-static STRING_CACHE: GILOnceCell<GILProtected<RefCell<PyStringCache>>> = GILOnceCell::new();
+static STRING_CACHE: OnceLock<Mutex<PyStringCache>> = OnceLock::new();
 
-macro_rules! get_string_cache {
-    ($py:ident) => {
-        STRING_CACHE
-            .get_or_init($py, || GILProtected::new(RefCell::new(PyStringCache::default())))
-            .get($py)
-    };
+#[inline]
+fn get_string_cache() -> &'static Mutex<PyStringCache> {
+    STRING_CACHE.get_or_init(|| Mutex::new(PyStringCache::default()))
 }
 
-pub fn cache_usage(py: Python) -> usize {
-    get_string_cache!(py).borrow().usage()
+pub fn cache_usage() -> usize {
+    get_string_cache()
+        .lock()
+        .expect("no code panics with mutex locked")
+        .usage()
 }
 
-pub fn cache_clear(py: Python) {
-    get_string_cache!(py).borrow_mut().clear();
+pub fn cache_clear() {
+    get_string_cache()
+        .lock()
+        .expect("no code panics with mutex locked")
+        .clear();
 }
 
 pub fn cached_py_string<'py>(py: Python<'py>, s: &str, ascii_only: bool) -> Bound<'py, PyString> {
     // from tests, 0 and 1 character strings are faster not cached
     if (2..64).contains(&s.len()) {
-        get_string_cache!(py).borrow_mut().get_or_insert(py, s, ascii_only)
+        get_string_cache()
+            .lock()
+            .expect("no code panics with mutex locked")
+            .get_or_insert(py, s, ascii_only)
     } else {
         pystring_fast_new(py, s, ascii_only)
     }