Short answer. Yes, presumptively. Article 1602 of the Civil Code presumes a sale with right to repurchase is really an equitable mortgage when, upon or after the expiration of the right to repurchase, another instrument extending the redemption period or granting a new period is executed. Signing that extension points toward a mortgage, not a completed sale.
What the law says
The contract shall be presumed to be an equitable mortgage, in any of the following cases
Civil Code, Article 1602 — When a Sale Is Really a Mortgage. Read the full provision →
What the law says
When upon or after the expiration of the right to repurchase another instrument extending the period of redemption or granting a new period is executed
Civil Code, Article 1602 — When a Sale Is Really a Mortgage. Read the full provision →
Why a late extension is treated with suspicion
Article 1602 lists several circumstances that trigger a presumption that a sale with right to repurchase is actually an equitable mortgage. One of them applies directly to your situation: when upon or after the expiration of the right to repurchase, another instrument extending the period of redemption or granting a new period is executed. A genuine, completed sale would not normally need a later document reviving or extending a redemption right that had already lapsed; needing to do so suggests the parties never really treated the earlier transaction as a final transfer of ownership.
What this presumption means for your transaction
Because this circumstance is expressly listed in Article 1602, signing that new instrument after the original repurchase period lapsed is enough, on its own, to trigger the presumption that your sale is an equitable mortgage rather than a true sale. This does not automatically decide the matter, since the presumption can still be addressed with other evidence, but it shifts the starting point strongly toward treating the arrangement as security for a debt rather than as ownership that had already passed to the buyer.
What follows if the presumption applies
If your transaction is treated as an equitable mortgage, Article 1602 also affects how anything the buyer received as rent or otherwise is characterized: any money, fruits, or other benefit received by the buyer is treated as interest, subject to the laws on usury, rather than as income from owning the property outright. The buyer in that scenario functions as a lender holding the property as security, and you retain the substantive position of a debtor rather than someone who permanently gave up the property.
Other circumstances that can reinforce this presumption
Article 1602 lists several other situations alongside this one, such as an unusually inadequate price, the seller remaining in possession, the buyer retaining part of the purchase price, or the seller continuing to pay the property's taxes. If any of those additional circumstances are also present in your transaction, that generally strengthens the case that the arrangement is an equitable mortgage rather than a genuine sale, on top of the late extension instrument you already signed after the redemption period had lapsed.