Short answer. Generally yes. Article 1297 of the Civil Code says that if the new obligation is void, the original one subsists — unless the parties intended the old relation to be extinguished in any event, regardless of whether the replacement turned out to be valid.
What the law says
If the new obligation is void, the original one shall subsist, unless the parties intended that the former relation should be extinguished in any event.
Civil Code, Article 1297 — Void New Obligation. Read the full provision →
A void replacement generally does not extinguish the original debt
Article 1297 addresses exactly this situation: a new obligation was set up to take the place of an old one, but the new one turns out to be void. The default outcome is that the original obligation shall subsist. The logic behind this is that a void obligation is treated in law as though it never validly existed, so if it never validly existed, it could not have actually replaced anything — the debt it was meant to substitute stays in place.
The exception: intending extinguishment 'in any event'
The article carves out one situation where the original debt does not survive: where the parties intended that the former relation should be extinguished in any event. That phrase describes an agreement where the parties meant to end the old obligation no matter what happened to the new one — even accepting the risk that the replacement might fail. Whether that intention existed depends on what the parties actually agreed to, not on how the substitution is labeled.
Why this distinction is not just technical
The difference between the default rule and this exception can decide whether you still owe anything at all. Under the default, a void replacement leaves you back where you started, still bound by the original debt. Under the exception, the creditor took on the risk of the new arrangement failing and cannot fall back on the old obligation. Which one governs your situation is a question of what was actually intended when the new arrangement was made, not something either side can simply assert after the fact.
What to check if you are in this situation
Look closely at whatever documentation exists around the substitution — was there any language showing the parties meant to cut ties with the old debt regardless of what happened to the new one, or was the new arrangement simply assumed to be a straightforward replacement? That evidence is what will determine which rule in Article 1297 applies to you, and it is worth reviewing with a lawyer before assuming either outcome. The article says nothing about a new obligation that is merely voidable rather than void — that different defect is governed by separate rules on annullable contracts.