Short answer. You do, as the buyer, if the improvement happened by nature or by time — the Civil Code says such improvement inures to the creditor's benefit. But if the seller spent money improving it, the seller's rights are instead limited to what a usufructuary would get.
What the law says
In case of loss, deterioration or improvement of the thing before its delivery, the rules in article 1189 shall be observed, the vendor being considered the debtor.
Civil Code, Article 1538 — Loss/Improvement Before Delivery. Read the full provision →
Article 1538 borrows its rules from elsewhere
Article 1538 does not spell out its own rule for improvement before delivery — it incorporates the rules of Article 1189, which normally governs what happens to a thing while an obligation is pending on a suspensive condition. Article 1538 applies those same rules to a sale, with one clarification: for this purpose, the vendor is considered the debtor — the party who owes the delivery of the thing to the buyer.
Improvement by nature or by time favors the buyer
Article 1189 states that if the thing is improved by its nature, or by time, the improvement shall inure to the benefit of the creditor. Applied to a sale, the buyer is the creditor — the one owed delivery — so an improvement that happens naturally, without anyone spending money to bring it about, belongs to the buyer once delivered. If the thing you bought simply became more valuable on its own before delivery, that increase in value is yours.
Improvement at the seller's expense is different
The rule changes where the improvement was made at the expense of the debtor — here, the seller. In that situation, Article 1189 gives the debtor no other right than that granted to the usufructuary. This means the seller who spent money improving the thing before delivery does not simply get to keep the improvement or demand its full value back as a matter of course; the seller's entitlement is limited to whatever rights the law gives a usufructuary in a similar position.
Why this distinction matters to you as the buyer
The answer to who benefits genuinely depends on the source of the improvement, not just the fact that the thing became more valuable. An improvement that occurred naturally or with the passage of time favors you as the buyer outright. An improvement the seller paid for is treated more cautiously, limiting the seller's claim rather than automatically shifting the benefit — or its cost — onto you. Because Article 1538 borrows wholesale from Article 1189, the same reasoning that governs a thing pending on a suspensive condition carries over directly into your sale, so it helps to trace which of that article's rules actually applies to your situation before assuming either party automatically keeps the increase.
Related provisions
- Civil Code, Article 1538 — Loss/Improvement Before Delivery
- Civil Code, Article 1189 — Loss, Deterioration, Improvement Pending a Suspensive Condition