diff -up bash-4.3/builtins/read.def.old bash-4.3/builtins/read.def
--- bash-4.3/builtins/read.def.old	2015-07-15 11:12:13.884695357 +0200
+++ bash-4.3/builtins/read.def	2015-07-15 11:10:55.339537361 +0200
@@ -794,6 +794,8 @@ assign_vars:
       else
 	var = bind_variable ("REPLY", input_string, 0);
       VUNSETATTR (var, att_invisible);
+      if (readonly_p (var) || noassign_p (var))
+       retval = EXECUTION_FAILURE;
 
       xfree (input_string);
       return (retval);