diff --git a/instant-distance-py/src/lib.rs b/instant-distance-py/src/lib.rs
index 5f74d90..eb976c2 100644
--- a/instant-distance-py/src/lib.rs
+++ b/instant-distance-py/src/lib.rs
@@ -8,7 +8,7 @@ use instant_distance::Point;
 use pyo3::conversion::IntoPy;
 use pyo3::exceptions::{PyTypeError, PyValueError};
 use pyo3::proc_macro::{pyclass, pymethods, pymodule, pyproto};
-use pyo3::types::{PyList, PyModule};
+use pyo3::types::{PyList, PyModule, PyString};
 use pyo3::{
     Py, PyAny, PyErr, PyIterProtocol, PyObject, PyObjectProtocol, PyRef, PyRefMut, PyResult, Python,
 };
@@ -28,19 +28,24 @@ fn instant_distance(_: Python, m: &PyModule) -> PyResult<()> {
 
 #[pyclass]
 struct HnswMap {
-    inner: instant_distance::HnswMap<FloatArray, String>,
+    inner: instant_distance::HnswMap<FloatArray, MapValue>,
 }
 
 #[pymethods]
 impl HnswMap {
     /// Build the index
     #[staticmethod]
-    fn build(points: &PyList, values: Vec<String>, config: &Config) -> PyResult<Self> {
+    fn build(points: &PyList, values: &PyList, config: &Config) -> PyResult<Self> {
         let points = points
             .into_iter()
             .map(FloatArray::try_from)
             .collect::<Result<Vec<_>, PyErr>>()?;
 
+        let values = values
+            .into_iter()
+            .map(MapValue::try_from)
+            .collect::<Result<Vec<_>, PyErr>>()?;
+
         let hsnw_map = instant_distance::Builder::from(config).build(points, values);
         Ok(Self { inner: hsnw_map })
     }
@@ -49,7 +54,7 @@ impl HnswMap {
     #[staticmethod]
     fn load(fname: &str) -> PyResult<Self> {
         let hnsw_map =
-            bincode::deserialize_from::<_, instant_distance::HnswMap<FloatArray, String>>(
+            bincode::deserialize_from::<_, instant_distance::HnswMap<FloatArray, MapValue>>(
                 BufReader::with_capacity(32 * 1024 * 1024, File::open(fname)?),
             )
             .map_err(|e| PyValueError::new_err(format!("deserialization error: {:?}", e)))?;
@@ -400,4 +405,25 @@ impl Point for FloatArray {
     }
 }
 
+#[derive(Clone, Deserialize, Serialize)]
+enum MapValue {
+    String(String),
+}
+
+impl TryFrom<&PyAny> for MapValue {
+    type Error = PyErr;
+
+    fn try_from(value: &PyAny) -> Result<Self, Self::Error> {
+        Ok(MapValue::String(value.extract::<String>()?))
+    }
+}
+
+impl IntoPy<Py<PyAny>> for &'_ MapValue {
+    fn into_py(self, py: Python<'_>) -> Py<PyAny> {
+        match self {
+            MapValue::String(s) => PyString::new(py, s).into(),
+        }
+    }
+}
+
 const DIMENSIONS: usize = 300;