diff --git a/scripts/kconfig/expr.c b/scripts/kconfig/expr.c
index 65531a7..0010034 100644
--- a/scripts/kconfig/expr.c
+++ b/scripts/kconfig/expr.c
@@ -64,7 +64,7 @@
 	return e2 ? expr_alloc_two(E_OR, e1, e2) : e1;
 }
 
-struct expr *expr_copy(struct expr *org)
+struct expr *expr_copy(const struct expr *org)
 {
 	struct expr *e;
 
diff --git a/scripts/kconfig/expr.h b/scripts/kconfig/expr.h
index 184eb6a..218991b 100644
--- a/scripts/kconfig/expr.h
+++ b/scripts/kconfig/expr.h
@@ -191,7 +191,7 @@
 struct expr *expr_alloc_comp(enum expr_type type, struct symbol *s1, struct symbol *s2);
 struct expr *expr_alloc_and(struct expr *e1, struct expr *e2);
 struct expr *expr_alloc_or(struct expr *e1, struct expr *e2);
-struct expr *expr_copy(struct expr *org);
+struct expr *expr_copy(const struct expr *org);
 void expr_free(struct expr *e);
 int expr_eq(struct expr *e1, struct expr *e2);
 void expr_eliminate_eq(struct expr **ep1, struct expr **ep2);