diff --git a/releasenotes.md b/releasenotes.md
index 5844cdf5b..04d0b6f93 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -72,6 +72,7 @@
 - Deref subscripts as needed for macro ref method arguments. #1789
 - Change ordering to simplify adding methods to type in conditional modules.
 - `#foo` style arguments were not type checked when given a type. #1790
+- Bug when using +++ on value build a slice or array: the rhs cast was not done.
 
 ### Stdlib changes
 - Increase BitWriter.write_bits limit up to 32 bits.
diff --git a/src/compiler/sema_const.c b/src/compiler/sema_const.c
index 22d14aecb..7aa182d2c 100644
--- a/src/compiler/sema_const.c
+++ b/src/compiler/sema_const.c
@@ -243,6 +243,7 @@ static bool sema_append_const_array_one(SemaContext *context, Expr *expr, Expr *
 	ConstInitializer *init = is_slice ? list->const_expr.slice_init : list->const_expr.initializer;
 	unsigned len = sema_len_from_const(list) + 1;
 	Type *indexed = type_get_indexed_type(init->type);
+	if (!cast_implicit(context, element, indexed, false)) return false;
 	Type *new_inner_type = is_vector ? type_get_vector(indexed, len) : type_get_array(indexed, len);
 	Type *new_outer_type = list->type;
 	if (!is_slice)