diff --git a/src/compiler/number.c b/src/compiler/number.c
index a32f9a0b8..21fa2c527 100644
--- a/src/compiler/number.c
+++ b/src/compiler/number.c
@@ -53,7 +53,7 @@ void expr_contract_array(ExprConst *expr_const, ConstKind contract_type)
 {
 	if (expr_const->const_kind == CONST_SLICE && !expr_const->slice_init)
 	{
-		*expr_const = (ExprConst) { .const_kind = contract_type };
+		*expr_const = (ExprConst) { .const_kind = contract_type, .bytes.ptr = NULL, .bytes.len = 0 };
 		return;
 	}
 	ASSERT(expr_const->const_kind == CONST_INITIALIZER || expr_const->const_kind == CONST_SLICE);
diff --git a/src/compiler/sema_const.c b/src/compiler/sema_const.c
index bdbc9d798..b7a0198c5 100644
--- a/src/compiler/sema_const.c
+++ b/src/compiler/sema_const.c
@@ -145,6 +145,7 @@ static bool sema_concat_bytes_and_other(SemaContext *context, Expr *expr, Expr *
 {
 	ArraySize len = left->const_expr.bytes.len;
 	bool is_bytes = left->const_expr.const_kind == CONST_BYTES;
+	ASSERT(is_bytes || left->const_expr.const_kind == CONST_STRING);
 	Type *indexed = type_get_indexed_type(left->type);
 	const char *left_bytes = left->const_expr.bytes.ptr;
 RETRY:;