--- a/src/ast_convert.rs
+++ b/src/ast_convert.rs
@@ -1,6 +1,6 @@
-use python_ast::{Module, stmt, expr, expr_context, cmpop, boolop, operator, unaryop, arguments, arg, alias, comprehension, keyword, withitem, excepthandler, slice};
+use python_ast::{Module, stmt, expr, expr_context, cmpop, boolop, operator, unaryop, arguments, arg, alias, comprehension, keyword, withitem, excepthandler, slice, name_constant};
 
-use cpython::{Python, PyObject};
+use cpython::{Python, PyObject, PyBool, PyResult};
 use cpython::ObjectProtocol; //for call method
 
 fn get_str(py: Python, object: PyObject) -> String {
@@ -369,8 +369,19 @@ fn parse_expr(py: Python, ast: PyObject)
         expr::Name(id, get_ctx(py, ast))
     } else if is_instance(&ast, &name_constant_type) {
         let value = ast.getattr(py, "value").unwrap();
-        let value = get_str(py, value);
-        expr::NameConstant(value)
+        let boolean: PyResult<PyBool> = value.extract(py);
+        let constant = match boolean {
+            Ok(boolean) => if boolean.is_true() {
+                name_constant::True
+            } else {
+                name_constant::False
+            },
+            Err(_) => {
+                assert!(value == py.None());
+                name_constant::None_
+            }
+        };
+        expr::NameConstant(constant)
     } else if is_instance(&ast, &num_type) {
         let n = ast.getattr(py, "n").unwrap();
         let n = get_str(py, n);