diff --git a/pyrsistent/_immutable.py b/pyrsistent/_immutable.py
index 66060d0..7c75945 100644
--- a/pyrsistent/_immutable.py
+++ b/pyrsistent/_immutable.py
@@ -98,6 +98,6 @@ def set(self, **kwargs):
     try:
         exec(template, namespace)
     except SyntaxError as e:
-        raise SyntaxError(e.message + ':\n' + template) from e
+        raise SyntaxError(str(e) + ':\n' + template) from e
 
     return namespace[name]