diff --git a/Cargo.toml b/Cargo.toml
index 2db2a73..32b8650 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ome-metadata"
-version = "0.3.0"
+version = "0.3.1"
 edition = "2024"
 rust-version = "1.85.1"
 authors = ["Wim Pomp <w.pomp@nki.nl>"]
diff --git a/src/lib.rs b/src/lib.rs
index 0a1fe87..cfaa233 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,7 +1,7 @@
 #![allow(non_camel_case_types)]
 pub mod ome;
 
-mod error;
+pub mod error;
 #[cfg(feature = "python")]
 mod py;
 
diff --git a/src/py.rs b/src/py.rs
index 1021419..ac443ad 100644
--- a/src/py.rs
+++ b/src/py.rs
@@ -6,6 +6,14 @@ use crate::ome::{
 use pyo3::exceptions::PyValueError;
 use pyo3::prelude::*;
 
+
+impl From<crate::error::Error> for PyErr {
+    fn from(err: crate::error::Error) -> PyErr {
+        PyErr::new::<PyValueError, _>(err.to_string())
+    }
+}
+
+
 macro_rules! impl_enum_into_py_object {
     ($($s:ident: $t:ty $(,)?)*) => {
         $(
@@ -27,7 +35,7 @@ macro_rules! impl_enum_into_py_object {
                 /// convert a value between units
                 fn convert(&self, unit: &str, value: f64) -> PyResult<f64> {
                     match unit.parse() {
-                        Ok(unit) => Ok(self.inner.convert(&unit, value).map_err(|e| PyErr::new::<PyValueError, _>(format!("{}", e)))?),
+                        Ok(unit) => Ok(self.inner.convert(&unit, value)?),
                         Err(_) => Err(PyErr::new::<PyValueError, _>(format!("Invalid unit: {}", unit)))
                     }
                 }
@@ -86,8 +94,7 @@ fn ome_metadata_rs(m: &Bound<'_, PyModule>) -> PyResult<()> {
 
     #[pyfn(m)]
     fn ome(text: &str) -> PyResult<Ome> {
-        text.parse()
-            .map_err(|e| PyErr::new::<PyValueError, _>(format!("{}", e)))
+        Ok(text.parse()?)
     }
 
     Ok(())