--- a/src/ast_convert.rs
+++ b/src/ast_convert.rs
@@ -4,6 +4,10 @@ use cpython::{Python, PyObject, PyBool, 
 use cpython::ObjectProtocol; //for call method
 
 fn get_str(py: Python, object: PyObject) -> String {
+    object.extract(py).unwrap()
+}
+
+fn convert_to_str(py: Python, object: PyObject) -> String {
     let pystring = object.str(py).unwrap();
     let mut string = pystring.to_string(py).unwrap();
     string.to_mut().to_string()
@@ -384,7 +388,9 @@ fn parse_expr(py: Python, ast: PyObject)
         expr::NameConstant(constant)
     } else if is_instance(&ast, &num_type) {
         let n = ast.getattr(py, "n").unwrap();
-        let n = get_str(py, n);
+        // FIXME: we should convert these to either bigint, double or complex.
+        // TODO: find a suitable bigint library.
+        let n = convert_to_str(py, n);
         expr::Num(n)
     } else if is_instance(&ast, &str_type) {
         let s = ast.getattr(py, "s").unwrap();