diff --git a/pyckel/src/lib.rs b/pyckel/src/lib.rs
index 6257b2fb..3550c56b 100644
--- a/pyckel/src/lib.rs
+++ b/pyckel/src/lib.rs
@@ -1,11 +1,21 @@
 use std::io::Cursor;
 
-use nickel_lang::{eval::cache::CBNCache, program::Program, serialize};
+use nickel_lang::{
+    error::Error,
+    eval::cache::{CBNCache, Cache},
+    program::Program,
+    serialize,
+};
 
 use pyo3::{create_exception, exceptions::PyException, prelude::*};
 
 create_exception!(pyckel, NickelException, PyException);
 
+/// Turn a Nickel (Rust) error into a NickelException (Python)
+fn error_to_exception<E: Into<Error>, EC: Cache>(error: E, program: &mut Program<EC>) -> PyErr {
+    NickelException::new_err(program.report_as_str(error.into()))
+}
+
 /// Evaluate from a Python str of a Nickel expression to a Python str of the resulting JSON.
 #[pyfunction]
 pub fn run(s: String) -> PyResult<String> {
@@ -14,13 +24,13 @@ pub fn run(s: String) -> PyResult<String> {
 
     let term = program
         .eval_full()
-        .map_err(|err| NickelException::new_err(program.report_as_str(err)))?;
+        .map_err(|error| error_to_exception(error, &mut program))?;
 
     serialize::validate(serialize::ExportFormat::Json, &term)
-        .map_err(|err| NickelException::new_err(program.report_as_str(err)))?;
+        .map_err(|error| error_to_exception(error, &mut program))?;
 
     let json_string = serialize::to_string(serialize::ExportFormat::Json, &term)
-        .map_err(|err| NickelException::new_err(program.report_as_str(err)))?;
+        .map_err(|error| error_to_exception(error, &mut program))?;
 
     Ok(json_string)
 }