diff --git a/Python/errors.c b/Python/errors.c
index 29f3cfd..a1ab4b8 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -124,7 +124,7 @@
 void
 err_setstr(exception, string)
 	object *exception;
-	char *string;
+	const char *string;
 {
 	object *value = newstringobject(string);
 	err_setval(exception, value);