--- /dev/null
+/* Redeclaration of parameters is an error. PR 13728. */
+/* { dg-do compile } */
+
+void f (int fred, /* { dg-error "previous definition" "" } */
+ int fred); /* { dg-error "redefinition of parameter" "" } */
+
+void f2 (int fred, /* { dg-error "previous definition" "" } */
+ int fred) /* { dg-error "redefinition of parameter" "" } */
+{
+}